Mathis on Graphene? Any hints?

Just wanted to examine how "Graphene" is expressed in the Charge Field.  This apparently is a high focus area of research at the moment.

I think I found something on this:
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http://milesmathis.com/desig.pdf

110c - Designer Electrons are really Photons

by Miles Mathis
Today's news [March 17, 2012] included a report from the National Accelerator Laboratory SLAC that “designer electrons” were being created in manufactured structures that resembled graphene. The interesting sentence is this one:

Initially, the electrons in this structure had graphene-like properties; for example, unlike ordinary electrons, they had no mass and traveled as if they were moving at the speed of light in a vacuum. But researchers were then able to tune these electrons in ways that are difficult to do in real graphene.

According to current theory, there should be no such beast as a designer electron. This shouldn't be happening, and yet they are selling it to you as no big deal. Yes, it is sold as a big deal as a matter of high-tech, but it is not being sold as the theory-ender it is. The electron is one of the fundamental particles of QM and QED, and beyond the Relativity transforms it cannot vary. You cannot do a Relativity transform on an electron to give it no mass or a speed of c. If you take an electron to a velocity of c, it has infinite mass, not zero mass. So these people at SLAC should know this isn't initially an electron. Since it has the properties of a photon—speed c and zero mass—why are they calling it an electron here?

Because:

By writing complex patterns that mimicked changes in carbon-carbon bond lengths and strengths in graphene, the researchers were able to restore the electrons’ mass in small, selected areas.

You can't do that with photons, they think, so these must be electrons. But what is happening is that the created photons are being re-energized up to the electron level, using my spin stacking method. We are seeing in the experiment the actual making of an electron from a photon. We are seeing proof of my particle unification, which shows that the photon and electron are the same particle, one with more spins than the other.

Although this should be fairly obvious to anyone doing even a quick scan of the data, the researchers won't go there as a matter of theory. Why? One, because they don't have the theory to cover it. You can't turn a photon that is a point particle into an electron, and their photon is a point particle. Two, because to admit it would bring down QM and QED from the foundations. So they simply gloss over it. They imply that this isn't a problem by not even mentioning it. They toot the horns on the high-tech side, while hiding the theory side completely.

Even more amazing is this:

“One of the wildest things we did was to make the electrons think they are in a huge magnetic field when, in fact, no real field had been applied, ”Manoharan said. They calculated the positions where carbon atoms in graphene should be, to make its electrons believe they were being exposed to magnetic fields ranging from zero to 60 Tesla, more than 30 percent higher than the strongest continuous magnetic field ever achieved on Earth. The researchers then moved carbon monoxide molecules to steer the electrons into precisely those positions, and the electrons responded by behaving exactly as predicted — as if they had been exposed to a real field.

Notice that we get no commentary on that, just that it is “wild.” But again, it completely overthrows the current model. How can positions alone create fields of 60 Tesla?

No answer from SLAC, but I can tell you. It is because SLAC is ignoring the charge field, as usual. I just showed how they ignore charge in accelerators, and they are doing it again here. To see what I mean, we can return for a moment to a recent paper of mine on the heliospheric current sheet, where we see them ignoring the electrical current of space. I do the simple math, showing that the number, though low, indicates an underlying charge field strength the equivalent of at least 3 million lightning bolts. We have the same thing here, with a magnetic field of 60 Tesla being created “from nothing.” The researchers can't get it through their heads that the created magnetic field is real, even after they measure it. They say that it is “as if” they had been exposed to a real field. But quanta don't react “as if” they are in a field. They either are or they are not. This isn't psychology, this is physics. Check the spelling! Given that the field is being created, the question is, “HOW is it being created?” Current theory has no way to explain it, which is precisely why we have to be told it is a mirage. You don't have to explain mirages, right? So the electrons are just “fooled.”

But the field is real. The magnetic field of 60 Tesla is there. Where did it come from? It comes from the charge field. As I have been screaming for years, charge exists even in the absence of ions. Photons are there even when no ions are present to create the E/M fields we measure. So there are unmeasured photon potentials existing at all times. To see how these are created, you have to study my nuclear diagrams, which show how atoms recycle this charge field, creating the underlying potentials.

What this means in this current experiment is that the spacing of the carbon monoxide in the molecular structure is creating the potentials that then energize these photon/electrons. We are seeing part of the great power tied up in the charge field.

This is not zero-point energy, although like this energy, zero-point energy is coming from the charge field. There is no zero-point energy. Zero-point energy is a made-up term, used to fill a hole in current theory. Because current theory has forgotten about charge, it needs manufactured ideas like zero-point energy and dark energy to fill the gap.
Again, charge is made up of real photons with real radii and real mass. They are not virtual and they are not point particles. They create real potentials, just like wind does. And charge is much “heavier” than anyone understands. In fact, photonic matter outweighs baryonic matter by 19 to 1.

Although I am told daily that there is no evidence for my theories, there is evidence for it on a daily basis, more each week.

Here's a recent paper on "Klein tunnelling in graphene":

http://www.europhysicsnews.org/component/content/article?id=313
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How massless electrons tunnel through graphene (Vol. 43 No. 2)

Klein tunnelling in one dimension. An electron incident from the left on a sharp potential step (the blue arrow indicates its direction of motion)

Electrons moving in graphene behave in an unusual way, as demonstrated by 2010 Nobel Prize laureates for physics A. Geim and K. Novoselov, who performed transport experiments on this one-carbon-atom-thick material. The present review explores the theoretical and experimental results to date of electrons tunnelling through energy barriers in graphene.

What could partly explain graphene's properties is that electrons travelling inside the material behave as if they were massless. Their behaviour is described by the so-called Dirac equation, which is normally used for high-energy particles such as neutrinos in vacuum moving at a velocity 300 times greater than that of electrons, nearing the speed of light.

In this review, the authors focus on the tunnelling effect occurring when Dirac electrons found in graphene are transmitted through different types of energy barriers. Contrary to the laws of classical mechanics, which govern larger scale particles that cannot cross energy barriers, electron tunnelling is possible in quantum mechanics - though only under restricted conditions, depending on the width and energy height of the barrier.

However, the Dirac electrons found in graphene can tunnel through energy barriers regardless of their width and energy height; a phenomenon called Klein tunnelling, described theoretically for 3D massive Dirac electrons by the Swedish physicist Oskar Klein in 1929. Graphene was the first material in which Klein tunnelling was observed experimentally, as massive Dirac electrons required energy barriers too large to be observed.

Klein tunnelling in graphene: optics with massless electrons
P.E. Allain and J.N. Fuchs, Eur. Phys. J. B 83, 301 (2011)

Quote from Mathis'  48. The Born-Einstein Letters paper:

http://milesmathis.com/born.html
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Other passages also act as propaganda, even when letters are not being suppressed. In letter 60, Born paraphrases Dirac:

the difficulties of QED [like infinite renormalization] "lie partly in the fact that Schrodinger's equations, and not those of Heisenberg, were used as a starting point." Here is a direct quote from Dirac: "For the purpose of setting up QED, Schrodinger's is a bad theory, Heisenberg's a good one."

As a sort of clarification of this assertion, Born comments on Schrodinger's mechanics in this way:
"The common objection is that one needs waves in spaces of many dimensions, and this canot be visualized."

But later Born admits that "Schrodinger himself had shown the mathematical equivalence of wave and matrix mechanics." So there are two glaring contradictions here. First, if wave and matrix mechanics are mathematically equivalent, there can hardly be a great deal of difference in choosing between the two for setting up QED. Of two maths that are really equivalent, one can hardly be good and the other bad. In fact, the simpler and more transparent math should always be preferred, given equivalence. This certainly applies to Schrodinger's equations, not Heisenberg's. Second, it is interesting here that a lack of visualization is a minus for Schrodinger but a plus for Heisenberg. The Copenhagen Interpretation—which everyone knows is connected to matrix mechanics—forbids its adherents from trying to visualize quantum motions and interactions. They treat its mathematical purity as its main selling point: the fact that it cannot be visualized is its main esoteric draw. It must be accepted simply because the math demands it. But then these same purists turn around and complain that Schrodinger does not offer us an easy visualization? The double standard could not be more transparent.

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32. A Critique of General Relativity

http://milesmathis.com/gr.html


As an example of this, look at Paul Dirac's lead-in to the tensor calculus in his book General Theory of Relativity [1975]. He says,

One can easily imagine a curved two-dimensional space immersed in Euclidean three-dimensional space. In the same way, one can have a curved four-dimensional space immersed in a flat space of a larger number of dimensions. Such a curved space is called a Riemann space. A small region of it is approximately flat.1

That is his entire explanation of curved space. Afterwards he simply dives into the math. But his foundation is already cracked. First of all, a “curved two-dimensional space” is not two-dimensional. A curved two-dimensional space is three-dimensional, by definition. This mistake should already be a clue that Dirac is long on math and short on conceptual understanding and rigor. And it means that a curved four-dimensional space must be five-dimensional, in which case we need a variable and a variable assignment for this fifth dimension. We get neither from Dirac, and we have never gotten either from anyone else, including Einstein and Kaluza (Kaluza gave us the fifth variable but no assignment of it to any physical or temporal extension). Furthermore, Dirac's last sentence is necessary because he will use the calculus to do math in infinitesimal regions of Riemann space. But you can see that this is a sort of cheat: the mathematician postulates curvature and then ignores it by going to a tiny area where there is no curvature. I will have more to say about that later in this paper.

Graphene

http://www.graphenea.com/pages/graphene-properties

Graphene is, basically, a single atomic layer of graphite; an abundant mineral which is an allotrope of carbon that is made up of very tightly bonded carbon atoms organised into a hexagonal lattice. What makes graphene so special is its sp2 hybridisation and very thin atomic thickness (of 0.345Nm). These properties are what enable graphene to break so many records in terms of strength, electricity and heat conduction (as well as many others). Now, let’s explore just what makes graphene so special, what are its intrinsic properties that separate it from other forms of carbon, and other 2D crystalline compounds?

Fundamental Characteristics

Before monolayer graphene was isolated in 2004, it was theoretically believed that two dimensional compounds could not exist due to thermal instability when separated. However, once graphene was isolated, it was clear that it was actually possible, and it took scientists some time to find out exactly how. After suspended graphene sheets were studied by transmission electron microscopy, scientists believed that they found the reason to be due to slight rippling in the graphene, modifying the structure of the material. However, later research suggests that it is actually due to the fact that the carbon to carbon bonds in graphene are so small and strong that they prevent thermal fluctuations from destabilizing it.

Electronic Properties

One of the most useful properties of graphene is that it is a zero-overlap semimetal (with both holes and electrons as charge carriers) with very high electrical conductivity. Carbon atoms have a total of 6 electrons; 2 in the inner shell and 4 in the outer shell. The 4 outer shell electrons in an individual carbon atom are available for chemical bonding, but in graphene, each atom is connected to 3 other carbon atoms on the two dimensional plane, leaving 1 electron freely available in the third dimension for electronic conduction. These highly-mobile electrons are called pi (π) electrons and are located above and below the graphene sheet. These pi orbitals overlap and help to enhance the carbon to carbon bonds in graphene. Fundamentally, the electronic properties of graphene are dictated by the bonding and anti-bonding (the valance and conduction bands) of these pi orbitals.

Combined research over the last 50 years has proved that at the Dirac point in graphene, electrons and holes have zero effective mass. This occurs because the energy – movement relation (the spectrum for excitations) is linear for low energies near the 6 individual corners of the Brillouin zone. These electrons and holes are known as Dirac fermions, or Graphinos, and the 6 corners of the Brillouin zone are known as the Dirac points. Due to the zero density of states at the Dirac points, electronic conductivity is actually quite low. However, the Fermi level can be changed by doping (with electrons or holes) to create a material that is potentially better at conducting electricity than, for example, copper at room temperature.

Tests have shown that the electronic mobility of graphene is very high, with previously reported results above 15,000 cm2·V−1·s−1 and theoretically potential limits of 200,000 cm2·V−1·s−1 (limited by the scattering of graphene’s acoustic photons). It is said that graphene electrons act very much like photons in their mobility due to their lack of mass. These charge carriers are able to travel sub-micrometer distances without scattering; a phenomenon known as ballistic transport. However, the quality of the graphene and the substrate that is used will be the limiting factors. With silicon dioxide as the substrate, for example, mobility is potentially limited to 40,000 cm2·V−1·s−1.

Mechanical Strength

Another of graphene’s stand-out properties is its inherent strength. Due to the strength of its 0.142 Nm-long carbon bonds, graphene is the strongest material ever discovered, with an ultimate tensile strength of 130,000,000,000 Pascals (or 130 gigapascals), compared to 400,000,000 for A36 structural steel, or 375,700,000 for Aramid (Kevlar). Not only is graphene extraordinarily strong, it is also very light at 0.77milligrams per square metre (for comparison purposes, 1 square metre of paper is roughly 1000 times heavier). It is often said that a single sheet of graphene (being only 1 atom thick), sufficient in size enough to cover a whole football field, would weigh under 1 single gram.

What makes this particularly special is that graphene also contains elastic properties, being able to retain its initial size after strain. In 2007, Atomic force microscopic (AFM) tests were carried out on graphene sheets that were suspended over silicone dioxide cavities. These tests showed that graphene sheets (with thicknesses of between 2 and 8 Nm) had spring constants in the region of 1-5 N/m and a Young’s modulus (different to that of three-dimensional graphite) of 0.5 TPa. Again, these superlative figures are based on theoretical prospects using graphene that is unflawed containing no imperfections whatsoever and currently very expensive and difficult to artificially reproduce, though production techniques are steadily improving, ultimately reducing costs and complexity.

Optical Properties

Graphene’s ability to absorb a rather large 2.3% of white light is also a unique and interesting property, especially considering that it is only 1 atom thick. This is due to its aforementioned electronic properties; the electrons acting like massless charge carriers with very high mobility. A few years ago, it was proved that the amount of white light absorbed is based on the Fine Structure Constant, rather than being dictated by material specifics. Adding another layer of graphene increases the amount of white light absorbed by approximately the same value (2.3%). Graphene’s opacity of πα ≈ 2.3% equates to a universal dynamic conductivity value of G=e2/4ℏ (±2-3%) over the visible frequency range.

Due to these impressive characteristics, it has been observed that once optical intensity reaches a certain threshold (known as the saturation fluence) saturable absorption takes place (very high intensity light causes a reduction in absorption). This is an important characteristic with regards to the mode-locking of fibre lasers. Due to graphene’s properties of wavelength-insensitive ultrafast saturable absorption, full-band mode locking has been achieved using an erbium-doped dissipative soliton fibre laser capable of obtaining wavelength tuning as large as 30 nm.

In terms of how far along we are to understanding the true properties of graphene, this is just the tip of the iceberg. Before graphene is heavily integrated into the areas in which we believe it will excel at, we need to spend a lot more time understanding just what makes it such an amazing material. Unfortunately, while we have a lot of imagination in coming up with new ideas for potential applications and uses for graphene, it takes time to fully appreciate how and what graphene really is in order to develop these ideas into reality. This is not necessarily a bad thing, however, as it gives us opportunities to stumble over other previously under-researched or overlooked super-materials, such as the family of 2D crystalline structures that graphene has born.


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Graphene Supercapacitors

http://www.graphenea.com/pages/graphene-supercapacitors

Graphenea
Written By Jesus de La Fuente / CEO Graphenea / j.delafuente@graphenea.com

View Our Graphene Products / Read More Graphene Publications / Contact Us

Scientists have been struggling to develop energy storage solutions such as batteries and capacitors that can keep up with the current rate of electronic component evolution for a number of years. Unfortunately, the situation we are in now is that while we are able to store a large amount of energy in certain types of batteries, those batteries are very large, very heavy, and charge and release their energy relatively slowly. Capacitors, on the other hand, are able to be charged and release energy very quickly, but can hold much less energy than a battery. Graphene application developments though have lead to new possibilities for energy storage, with high charge and discharge rates, which can be made very cheaply. But before we go into specific details, it would be sensible to first outline the basics of energy storage and the potential goals of developing graphene as a supercapacitor.

Capacitors and supercapacitors explained

A capacitor is an energy storage medium similar to an electrochemical battery. Most batteries, while able to store a large amount of energy are relatively inefficient in comparison to other energy solutions such as fossil fuels. It is often said that a 1kg electrochemical battery is able to produce much less energy than 1 litre of gasoline; but this kind of comparison is extremely vague, mathematically illogical, and should be ignored. In fact, some electrochemical batteries can be relatively efficient, but that doesn’t get around the primary limiting factor in batteries replacing fossil fuels in commercial and industrial applications (for example, transportation); charge time.

High capacity batteries take a long time to charge. This is why electrically powered vehicles have not taken-off as well as we expected twenty or thirty years ago. While you are now able to travel 250 miles or more on one single charge in a car such as the Tesla Model S, it could take you over 43 hours to charge the vehicle using a standard 120v wall socket in order to drive back home. This is not acceptable for many car users. Capacitors, on the other hand, are able to be charged at a much higher rate, but store (as already mentioned) somewhat less energy.

Supercapacitors, also known as ultracapacitors, are able to hold hundreds of times the amount of electrical charge as standard capacitors, and are therefore suitable as a replacement for electrochemical batteries in many industrial and commercial applications. Supercapacitors also work in very low temperatures; a situation that can prevent many types of electrochemical batteries from working. For these reasons, supercapacitors are already being used in emergency radios and flashlights, where energy can be produced kinetically (by winding a handle, for example) and then stored in a supercapacitor for the device to use.

A conventional capacitor is made up of two layers of conductive materials (eventually becoming positively and negatively charged) separated by an insulator. What dictates the amount of charge a capacitor can hold is the surface area of the conductors, the distance between the two conductors and also the dielectric constant of the insulator. Supercapacitors are slightly different in the fact that they do not contain a solid insulator.

Instead the two conductive plates in a cell are coated with a porous material, most commonly activated carbon, and the cells are immersed in an electrolyte solution. The porous material ideally will have an extremely high surface area (1 gram of activated carbon can have an estimated surface area equal to that of a tennis court), and because the capacitance of a supercapacitor is dictated by the distance between the two layers and the surface area of the porous material, very high levels of charge can be achieved.

While supercapacitors are able to store much more energy than standard capacitors, they are limited in their ability to withstand high voltage. Electrolytic capacitors are able to run at hundreds of volts, but supercapacitors are generally limited to around 5 volts. However, it is possible to engineer a chain of supercapacitors to run at high voltages as long as the series is properly designed and controlled.

Graphene-based supercapacitors

Supercapacitors, unfortunately, are currently very expensive to produce, and at present the scalability of supercapacitors in industry is limiting the application options as energy efficiency is offset against cost efficiency. This is the reason why a paper by researchers at the UCLA has been so highly referred to within scientific circles and publications as they were able to produce supercapacitors made out of graphene by using a simple DVD LightScribe writer on a home PC. This idea of creating graphene monolayers by using thermo lithography is not necessarily a new one, as scientists from the US were able to produce graphene nanowires by using thermochemical nanolithography back in 2010; however, this new method avoids the use of an atomic force microscope in favour of a commercially available laser device that is already prevalent in many homes around the world.

Why are scientists looking at using graphene instead of the currently more popular activated carbon? Well, graphene is essentially a form of carbon, and while activated carbon has an extremely high relative surface area, graphene has substantially more. As we have already highlighted, one of the limitations to the capacitance of ultracapacitors is the surface area of the conductors. If one conductive material in a supercapacitor has a higher relative surface area than another, it will be better at storing electrostatic charge. Also, being a material made up of one single atomic layer, it is lighter. Another interesting point is that as graphene is essentially just graphite, which is a form of carbon, it is ecologically friendly, unlike most other forms of energy storage.

The efficiency of the supercapacitor is the important factor to bear in mind. In the past, scientists have been able to create supercapacitors that are able to store 150 Farads per gram, but some have suggested that the theoretical upper limit for graphene-based supercapacitors is 550 F/g. This is particularly impressive when compared against current technology: a commercially available capacitor able to store 1 Farad of electrostatic energy at 100 volts would be about 220mm high and weigh about 2kgs, though current supercapacitor technology is about the same, in terms of dimensions relative to energy storage values, as a graphene-based supercapacitor would be.

The future for graphene-based supercapacitors

Due to the lightweight dimensions of graphene based supercapacitors and the minimal cost of production coupled with graphene’s elastic properties and inherit mechanical strength, we will almost certainly see technology within the next five to ten years incorporating these supercapacitors. Also, with increased development in terms of energy storage limits for supercapacitors in general, graphene-based or hybrid supercapacitors will eventually be utilized in a number of different applications.

Vehicles that utilize supercapacitors are already prevalent in our society. One Chinese company is currently manufacturing buses that incorporate supercapacitor energy recovery systems, such as those used on Formula 1 cars, to store energy when braking and then converting that energy to power the vehicle until the next stop. Additionally, we will at some point in the next few years begin to see mobile telephones and other mobile electronic devices being powered by supercapacitors as not only can they be charged at a much higher rate than current lithium-ion batteries, but they also have the potential to last for a vastly greater length of time.

Other current and potential uses for supercapacitors are as power backup supplies for industry or even our own homes. Businesses can invest in power backup solutions that are able to store high levels of energy at high voltages, effectively offering full power available to them, to reduce the risk of having to limit production due to inadequate amounts of power. Alternatively, if you have a fuel cell vehicle that is able to store a large amount of electrical energy, then why not use it to help power your home in the event of a power outage?

We can expect that this scenario of using advanced energy storage and recovery solutions will become much more widely used in the coming years as the efficiency and energy density of supercapacitors increases, and the manufacturing costs decrease. While graphene-based supercapacitors are currently a viable solution in the future, technology needs to be developed to make this into a reality. But rest assured, many companies around the world are already trialling products using this technology and creating new ways to help subsidise the use of fossil-fuels and toxic chemicals in our ever-demanding strive for energy.

Looked at this article again on Graphene conversions. Mathis says that near graphene, the Charge Field could spin-up a photon to an electron.  Looks like this experiment may be doing this? (...also posted in Scientific Discoveries but reposted here.)
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April 14, 2015
Graphene pushes the speed limit of light-to-electricity conversion

http://phys.org/news/2015-04-graphene-limit-light-to-electricity-conversion.html
(more at link...)

ICFO researchers Klaas-Jan Tielrooij, Lukasz Piatkowski, Mathieu Massicotte and Achim Woessner led by ICFO Prof. Frank Koppens and ICREA Prof. at ICFO Niek van Hulst, in collaboration with scientists from the research group led by Pablo Jarillo-Herrero at MIT and the research group led by Jeanie Lau at UC Riverside, have now demonstrated that a graphene-based photodetector converts absorbed light into an electrical voltage at an extremely high speed. The study, entitled "Generation of photovoltage in graphene on a femtosecond timescale through efficient carrier heating", has recently been published in Nature Nanotechnology.

The new device that the researchers developed is capable of converting light into electricity in less than 50 femtoseconds (a twentieth of a millionth of a millionth of a second). To do this, the researchers used a combination of ultrafast pulse-shaped laser excitation and highly sensitive electrical readout. As Klaas-Jan Tielrooij comments, "the experiment uniquely combined the ultrafast pulse shaping expertise obtained from single molecule ultrafast photonics with the expertise in graphene electronics. Facilitated by graphene's nonlinear photo-thermoelectric response, these elements enabled the observation of femtosecond photodetection response times."

The ultrafast creation of a photovoltage in graphene is possible due to the extremely fast and efficient interaction between all conduction band carriers in graphene. This interaction leads to a rapid creation of an electron distribution with an elevated electron temperature. Thus, the energy absorbed from light is efficiently and rapidly converted into electron heat. Next, the electron heat is converted into a voltage at the interface of two graphene regions with different doping. This photo-thermoelectric effect turns out to occur almost instantaneously, thus enabling the ultrafast conversion of absorbed light into electrical signals. As Prof. van Hulst states, "it is amazing how graphene allows direct non-linear detecting of ultrafast femtosecond (fs) pulses".

From Mathis' "The Great Methane Stink":
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This new theory allows me to make several other predictions, ones that can be checked with current machines—as far as I know. I believe it should be possible to measure the charge being emitted laterally by the Carbon inside CO2, and I think it will be found to be different from the lateral emission of Carbon alone. In other words, we need CO2 in a solid (but still non-magnetic) state, and then we need to probe the Carbon in that molecule, mapping its lateral charge profile by some means. I believe we will find that the Carbon has a different nuclear make-up than Carbon alone. I think we will find that a single atom of Carbon has two alphas in its core, while an atom of Carbon in most molecules has one.

This ties into recent questions I have been asked about Fullerenes and irradiated graphites. It has been found that Carbon, although normally non-magnetic, can be very magnetic in some situations. I would suggest that the varying nuclear make-up of different forms of Carbon explains this in the most direct and mechanical way. It would appear that Carbon in compound with itself can re-arrange in the same way we saw it re-arranging in CO2, especially in an irradiated field or in long chains. Once you have two prongs on each end of Carbon and only one alpha in the core, this will create a spun-up through charge, which is what causes magnetism.

From the Period Four  paper:
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In closing, I need to tie up one weak spot. I have said that those inner holes needed to be filled in most cases, to prevent the charge field from dashing through there and causing dissolution. But if protons are working like fans, pushing charge through, how does that prevent dissolution? If charge going through is dangerous, pushing charge through even faster won't help, will it?

Actually, it does, and this is because the danger from charge going through those holes was incoherent and/or unfocused charge. With no protons channeling charge, you of course have unchanneled charge. What is unchanneled charge? It is charge with no real direction. If those holes are open, charge can be arriving from any direction, with any spin. It will then move into that axis alpha on any vector, and most of those vectors won't be through vectors. In other words, the charge will go into the alpha, but it won't pass straight through. It will get into the alpha from the side and cause all kinds of trouble, since it isn't channeled charge. That alpha is channeling up or down, and so this unruly charge from the side is a menace. But once you put a proton in that hole, you have channeled charge. The charge is both spin coherent and linearized, so it passes straight through that axis alpha with minimal effect. I won't say no effect, since we saw above that protons in those holes can diminish conduction by a small amount. But with protons in the inner holes, the nucleus is in no danger of dissolution. The charge passes straight through in an orderly way.

I have now fielded a good question from a reader. He asks, “Don't you have charge being affected in opposite ways here? When channeled charge passes through the axis level, you say it interferes with conduction. But then you say it 'boosts' charge in Selenium. Isn't interference the opposite of boosting? How can that work?” It works because Selenium isn't conducting. You get conduction with elements like Arsenic and Copper, which have different numbers of protons top and bottom. Or you can get magnetic conduction with elements like Iron, but then you need more protons in the axis than in the carousel. Neither of those things is true of Selenium. Therefore, when the crossing charge meets the main axis charge in Selenium, it can only boost the charge. Some charge gets captured, you see, which acts like a boost. Remember, the interference I was talking about with conduction is actually a capturing of charge as well. But because it is captured by charge that is being conducted through the axis instead of charge being channeled into the carousel level, it ends up lowering the total instead of increasing it. Just think about it: we add an equal amount of charge to the top and bottom inner holes. So the north charge is increased by the same amount as the south charge. But the south charge was twice as strong as the north to start with (because the south has two protons pulling in charge while the north has one). Therefore, after adding equal amounts to both, the north charge is no longer half the south. It is a tiny bit more than half. Which means when they meet, we now get a tiny bit more cancellation. The north charge is a tiny bit stronger than it was, so it cancels a bit more than half of the south charge, giving us less conduction. But since Selenium isn't conducting, it doesn't feel experience this cancellation. It only experiences the boost. When elements have equal numbers of protons north, south and in the carousel level, the axis charge is pulled into the carousel level from the nuclear center, and so it never crosses.

To read more about energy transfer by metals, you may now consult my newest paper on the Drude-Sommerfeld Model, where I show a new definition of heat capacity, among other things.

Also possibly relevant is this piece on "Han Purple" losing the third dimension like mono-layer Graphene. Like Graphene the "magnetism" changes as the temperature changes with barium copper silicate:
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Han Purple and the Third Dimension

Barium copper-silicate doesn't just have archaeologists and chemists intrigued. At normal temperatures, it's an insulator and is nonmagnetic. Along with its many fine properties - prettiness, historical importance, a hint of aristocratic style — barium copper-silicate has many electrons, some of which spin up and some of which are spin down.

Something unusual happens as the temperature drops and as a magnetic field is applied, although the temperature has to drop pretty far, going down to between one and three degrees Kelvin, and the magnetic field has to be about 800,000 times the strength of Earth's magnetic field. The results are worth it — the electrons seem to merge, taking on one spin, and acting as one electron.

That sounds like an ordinary superconductor, you say. Then you're as foolish as a Phoenician in sub-par purple! Han purple still has a trick up its sleeve. Drop the temperature some more and something happens to the magnetic wave traveling through the substance. At higher temperatures, it propagates like a regular wave, traveling in three dimensions. Get under one degree Kelvin, and it no longer has a vertical component. It propagates in two dimensions only.

Scientists think that this has something to do with the structure of barium copper silicate. It's components are arranged like layers of tiles, so they don't stack up neatly. Each layers' tiles are slightly out of sync with the layer below them. This may frustrate the wave and force it to go two dimensional.

https://milesmathis.forumotion.com/n48-new-findings-to-be-explained-with-the-charge-field

Team finds electricity can be generated by dragging saltwater over graphene
April 16, 2014 by Bob Yirka report

Read more at: http://phys.org/news/2014-04-team-electricity-saltwater-graphene.html#jCp
http://phys.org/journals/nature-nanotechnology/
http://www.nature.com/articles/nnano.2014.56
http://www.iflscience.com/technology/tweaked-graphene-could-double-electricity-generated-solar

Illustration of the experimental set-up. A liquid droplet is sandwiched between graphene and a SiO2/Si wafer, and drawn by the wafer at specific velocities. Inset: a droplet of 0.6 M NaCl solution on a graphene surface with advancing and receding contact angles of 91.98 and 60.28, respectively. Credit: Nature Nanotechnology (2014) doi:10.1038/nnano.2014.56

Read more at: http://phys.org/news/2014-04-team-electricity-saltwater-graphene.html#jCp

-------

(Phys.org) —A team of researchers at China's Nanjing University of Aeronautics and Astronautics, studying graphene properties, has discovered that the act of dragging saltwater over a piece of graphene can generate electricity. In their paper published in the journal Nature Nanotechnology, the team describes how in seeking to turn the idea of submerging carbon nanotubes in a flowing liquid to generate a voltage on its head, they came upon the idea of simply dragging water droplets across graphene instead.

Because of graphene's unique electrical properties, researchers have been hard at work trying to determine if it can be used to generate electricity at a lower cost (and in cleaner fashion) than conventional methods. To date, scientists have been using a technique whereby ionic fluids are pushed through different types of nanostructures—it works, but a pressure gradient must be used, which causes the approach to be inefficient. Others have looked at putting carbon nanotubes in moving water to capture electricity that is generated, but once again, a pressure gradient is needed. In this new effort, the researchers have found a way to generate electricity using graphene without the need for a pressure gradient, or any other mechanism other than gravity.

In their experiments, the researchers placed single drops of sea water (and other ionic solutions) on top of strips of monolayer graphene and then dragged them around. Doing so, they discovered, resulted in the generation of electricity—adding more drops or increasing the velocity of dragging increased the voltage.

To understand why, the team took a closer look. As it turned, out, the explanation was simple. When a saltwater drop sits still on top of a strip of graphene, any charge is redistributed symmetrically on both sides of the drop, leaving zero net potential difference between them. When the drop is moved, however, the distribution becomes unbalanced—electrons are desorbed at one end of the drop and absorbed at the other, generating a small amount of voltage—just 30mV—enough to allow the team to use it as part of a handwriting sensor and as part of an energy harvesting device.

Using the newly discovered technique to generate electricity isn't going to become a commercial proposition anytime soon, of course, as there is still the tricky problem of creating mass amounts of graphene at a reasonable price. But if that ever happens, people everywhere could very easily create their own electricity, as it appears the process is exceptionally scalable.

Explore further: Graphene battery demonstrated to power an LED

More information: Generating electricity by moving a droplet of ionic liquid along graphene, Nature Nanotechnology (2014) DOI: 10.1038/nnano.2014.56

Abstract
Since the early nineteenth century, it has been known that an electric potential can be generated by driving an ionic liquid through fine channels or holes under a pressure gradient. More recently, it has been reported that carbon nanotubes can generate a voltage when immersed in flowing liquids, but the exact origin of these observations is unclear, and generating electricity without a pressure gradient remains a challenge. Here, we show that a voltage of a few millivolts can be produced by moving a droplet of sea water or ionic solution over a strip of monolayer graphene under ambient conditions. Through experiments and density functional theory calculations, we find that a pseudocapacitor is formed at the droplet/graphene interface, which is driven forward by the moving droplet, charging and discharging at the front and rear of the droplet. This gives rise to an electric potential that is proportional to the velocity and number of droplets. The potential is also found to be dependent on the concentration and ionic species of the droplet, and decreases sharply with an increasing number of graphene layers. We illustrate the potential of this electrokinetic phenomenon by using it to create a handwriting sensor and an energy-harvesting device.

Journal reference: Nature Nanotechnology

Graphene Could Double Electricity Generated From Solar

January 26, 2015 | by Lisa Winter
Photo credit: scanrail/iStockphoto

The amount of sunlight that hits the Earth every 40 minutes is enough to meet global energy demands for an entire year. The trick, of course, is harnessing it and converting it into useful electricity. A new study has revealed that tweaking graphene allows it to generate two electrons for every photon of light it receives. This could double the amount of electricity currently converted in photovoltaic devices. Marco Grioni from École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland is one of the senior authors on the paper, which was published in Nano Letters.

Graphene is a monolayer of carbon atoms arranged in a honeycomb pattern. It is incredibly light, flexible, exponentially stronger than steel, and capable of conducting electricity even better than copper. In order to make it useful in photovoltaic devices, the researchers needed to have a better idea of graphene’s mechanism for converting light into electricity. This process takes only a femto-second (10-15 sec), which is too quick to easily study.

To learn more about how this energy conversion takes place, the graphene was subjected to a treatment called “ultrafast time- and angle-resolved photoemission spectroscopy” (trARPES). The material was placed in an ultra-high vacuum chamber and blasted with ultrafast laser light, which excited the electrons and made them more capable of carrying an electrical current. A second laser emitted pulses of light, recording the current energy level of each electron in each pulse. These images were then put together, kind of like a flip book, to portray the action that happens on such a short timescale.

The researchers facilitated the conversion process by ‘doping’ the graphene. That is, they improved the material’s photovoltaic prowess by chemically altering the number of electrons, thereby exciting them. When a photon comes and knocks an electron back to the ground state, that one electron is able to excite two more, generating the electric current.

“This indicates that a photovoltaic device using doped graphene could show significant efficiency in converting light to electricity,” says Marco Grioni.

Doped graphene appears to be a great material to easily release the electrons and use extra energy to excite other electrons, rather than waste the energy as heat. Unfortunately, the material needs a little help in absorbing light; a key requirement for photovoltaic devices. Graphene will need to be combined with other ultra-thin materials, such as tungsten diselenide or molybednium disulphide, like has been attempted in previous studies. This could possibly be the key in bumping solar energy conversion from its assumed plateau of 32% up to an astonishing 60%; an increase that could revolutionize solar energy. Moving forward, the researchers are planning to use similar measures to investigate the photovoltaic properties of other ultra-thin materials, including molybednium disulphide.

[Hat tip: EEE Spectrum]

http://www.iflscience.com/technology/tweaked-graphene-could-double-electricity-generated-solar

Found some interesting papers on the Hall effect at Room temperature with Graphene.  Miles had a paper back in July on the Hall Effect.  I think a good student of Mathis can crack this particular nut wide open:

The Hall Effect: a Charge Field Explanation.
I ditch electron holes, offering a logical and mechanical theory for the Hall Voltage.
http://milesmathis.com/hall.pdf
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The Quantum Hall Effect in Graphene
Daniel  G.  Flynn
Department of Physics, Drexel University, Philadelphia, PA
(Dated:  December 7, 2010)
http://www.physics.drexel.edu/~bob/TermPapers/Flynn_QuantumPaper.pdf (an interesting read).

Flynn wrote:
THE QUANTUM HALL EFFECT IN GRAPHENE

GRAPHENE

Graphene  is  a  single  layer  of  carbon  atoms  in  a
two-dimensional  hexagonal  lattice.   The  carbon  atoms
bond  to  one  another  via  covalent  bonds  leaving  one
2p  electron  per  carbon  atom  unbonded.   The  result  is
that  the  Fermi  surface  of  graphene  is  characterized  by
six  double  cones.   In  the  absence  of  applied  fields,  the
Fermi level is situated at the connection points of these
cones.  Since the density of electrons is zero at the Fermi
level,  the  electrical  conductivity  of  graphene  is  very
low.    However,  the  application  of  an  external  electric
field  can  change  the  Fermi  level  causing  graphene  to
behave as a semi-conductor.  In this case, near the Fermi
level  the  dispersion  relation  for  electrons  is  linear  and
the electrons behave as though they have zero effective
mass  (Dirac  fermions).   Because  graphene  exhibits  this
behavior  even  at  room  temperature,  it  is  observed  to
exhibit  both  the  integer  and  fractional  quantum  Hall
effect.

http://www.researchgate.net/publication/6501256_Room-Temperature_Quantum_Hall_Effect_in_Graphene

Quantum Hall Effect Observed At Room Temperature

Date:   February 16, 2007
Source: National High Magnetic Field Laboratory

Summary:
An international team of scientists is able to see the "shimmering quantum world" at ambient temperatures with the help of high magnetic fields and a fascinating material called graphene.

K.S. Novoselov1, Z. Jiang2, 3, Y. Zhang2, S.V. Morozov1, H.L. Storm er2, U. Zeitler4, J.C. Maan4, G.S. Boebinger3, P. Kim2* & A.K. Geim1*
1Departm ent of Physics, University of Manchester, M13 9PL, Manchester, UK
2Departm ent of Physics, Colum bia University, New York, New York 10027, USA
3National High Magnetic Field Laboratory, Tallahassee, Florida 32310, USA
4High Filed Magnet Laboratory, Radboud University Nijmegen, 6525 ED Nijmegen, Netherlands

Using the highest magnetic fields in the world, an international team of researchers has observed the quantum Hall effect -- a much studied phenomenon of the quantum world -- at room temperature.

The quantum Hall effect was previously believed to only be observable at temperatures close to absolute zero (equal to minus 459 degrees). But when scientists at the National High Magnetic Field Laboratory in the U.S. and at the High Field Magnet Laboratory in the Netherlands put a recently developed new form of carbon called graphene in very high magnetic fields, scientists were surprised by what they saw.

"At room temperature, these electron waves are usually destroyed by the jiggling atoms and the quantum effects are destroyed," said Nobel Prize winner Horst Stormer, physics professor at Columbia University and one of the paper's authors. "Only on rare occasions does this shimmering quantum world survive to the temperature scale of us humans."

The quantum Hall effect is the basis for the international electrical resistance standard used to characterize even everyday materials that conduct electricity, such as the copper wires in a home. It was first discovered in 1980 by the German physicist Klaus von Klitzing, who was awarded a Nobel Prize in 1985 for his discovery. Until recently the quantum Hall effect was considered to belong to the realm of very low temperatures.

That opinion began to change, however, with the ability to create very high magnetic fields and with the discovery of graphene, a single atomic sheet of atoms about as strong as diamond. Together, these two things have allowed scientists to push this fragile quantum effect all the way to room temperature. Now there is a way to see curious and often surprising quantum effects, such as frictionless current flow and resistances as accurate as a few parts per billion, even at room temperature.

The research was carried out by scientists from the University of Manchester in England, Columbia University in New York, the National High Magnetic Field Laboratory in Tallahassee, Florida, the High Field Magnet Laboratory in Nijmegen, Netherlands, and the Foundation for Fundamental Research on Matter, also in the Netherlands. Their article appears in Science Express, the advanced online publication of Science magazine, a top American journal with international stature.

The scientists believe that these findings may one day lead to a compact resistance standard working at elevated temperatures and magnetic fields that are easily attainable at the National High Magnetic Field Laboratory.

"The more we understand the strange world of quantum physics, the better we can design the next generation of ultra-small electrical devices, which already are pushing into the quantum regime," said Gregory S. Boebinger, director of the U.S. magnet lab.

"This is a really amazing discovery for a quantum Hall physicist," said Uli Zeitler, senior scientist at the High Field Magnet Laboratory. "For more than two decades, we've focused our research on exploring new frontiers such as very low temperatures and extremely sophisticated materials, and now it appears that we can just measure a quantum Hall effect in a pencil-trace and at room temperature."

The room temperature quantum Hall effect was discovered independently in the two high field labs, in the 45-tesla Hybrid magnet in Tallahassee and in a 33-tesla resistive magnet in Nijmegen. Both research groups agreed that a common announcement on both sides of the Atlantic was the right thing to do.

"Because so many scientists are exploring this exciting new material, we are all on this roller coaster together," said Boebinger. "Sometimes it makes sense to put competitiveness aside and write a better paper together."

In addition to Stormer, Boebinger and Zeitler, authors on the paper include Andre Geim and Kostya Novoselov of the University of Manchester; Philip Kim, Zhigang Jiang and Y. Zhang at Columbia, and Jan Kees Maan, director of the High Field Magnet Lab.

This work is supported by the National Science Foundation, the U.S. Department of Energy, the Microsoft Corp., and the W.M. Keck Foundation.

The National High Magnetic Field Laboratory develops and operates state-of-the-art, high-magnetic-field facilities that faculty and visiting scientists and engineers use for research. The laboratory is sponsored by the National Science Foundation and the state of Florida. To learn more, visit http://www.magnet.fsu.edu.



Also:
--------

Operation of graphene quantum Hall resistance standard in a cryogen-free table-top system

"One of the first properties observed in graphene was the QHE and it was immediately realised that it is ideal for metrology by virtue of its unique band structure [4] [5] [6] [7]. The Landau level quantisation in graphene is a lot stronger than in traditional semiconductor systems which implies that both a lower magnetic field can be used and that the low temperature constraint is more relaxed [6]. Following the original demonstration of high-accuracy quantum Hall resistance measurements in epitaxial graphene grown on SiC [8] and proof of the universality of the QHE between graphene and GaAs [9], recently these results have been very nicely reproduced by a number of different research groups [10] [11] [12]. "  

Operation of graphene quantum Hall resistance standard in a cryogen-free table-top system

Highly compressible 3D periodic graphene aerogel microlattices
http://www.nature.com/ncomms/2015/150422/ncomms7962/full/ncomms7962.html

Posted: Feb 09, 2015
3D-printing with graphene

(Nanowerk Spotlight) The successful implementation of graphene-based devices invariably requires the precise patterning of graphene sheets at both the micrometer and nanometer scale. It appears that 3D-printing techniques are an attractive fabrication route towards three-dimensional graphene structures. In a previous Nanowerk Spotlight we reported on the first 3D printed nanostructures made entirely of graphene.

There are also different methods to build 3D graphene monoliths – for example freeze casting or emulsion templating, etc. – but they are limited to building simple shapes, for example cylinders or cubes.



Using a different approach, researchers have now used flakes of chemically modified graphene – namely graphene oxide GO and its reduced form rGO – together with very small amounts of a responsive polymer (a polymer that changes behavior and conformation when a 'chemical switch' is activated), to formulate water based ink or pastes.
"Our formulations have the flow and physical properties we need for the filament deposition process required in 3D printing: They need to flow through very small nozzles and set immediately after passing through it, retaining the shape and holding the layers on top," Dr. Esther García-Tuñon, a Research Associate at the Centre for Advanced Structural Ceramics at Imperial College London (ICL), tells Nanowerk. "We use this two-dimensional material as building block to create macroscopic 3D structures and a technique called direct ink writing (DIW) also known as direct write assembly (DWA), or Robocasting."

http://www.nanowerk.com/spotlight/spotid=38965.php

García-Tuñon is first author of a paper in the January 21, 2015 online edition of Advanced Materials ("Printing in Three Dimensions with Graphene") where a team from ICL, the University of Warwick, the University of Bath, and the Universidad de Santiago de Compostela, describe their technique.

This technique is based on the continuous deposition of a filament following a computer design. The 3D structures are built layer by layer from bottom to top.

Electronic transport in graphene: towards high mobility  
K.   I.     BOLOTIN    ,     Vanderbilt  University ,   USA    
DOI:  10.1533/9780857099334.3.1991999
© 2014 Woodhead Publishing Limited

Abstract:   Strong carrier scattering perturbs the intrinsic response of
Dirac fermions in graphene and limits potential applications of
graphene-based devices. Multiple scattering mechanisms including
Coulomb scattering, lattice disorder scattering and electron–phonon
scattering play roles in realistic graphene devices. Moreover, different
types and preparations of graphene are characterized by different
dominant scattering mechanisms. In this chapter, we review the recent
progress towards reduction of carrier scattering in graphene. We start by
discussing different metrics – such as carrier mobility, mean free path,
and scattering time – that are used to quantify the scattering strength.
Then, we review the strategies to reduce scattering and to improve
carrier mobility. These strategies include: lowering defect density,
suspending graphene, depositing graphene onto high-quality substrates,
and covering it with high- k dielectrics. Finally, we briefl y address the
physical phenomena and device applications that are specific to
ultraclean high-mobility graphene.  

http://scitechconnect.elsevier.com/wp-content/uploads/2014/06/Graphene-Skakalova-ch9.pdf

210 Graphene
9.4.3
Electron–phonon scattering
---------------
Quantum Hall conductance of graphene combined with charge-trap memory operation

Haeyong Kang1,3, Yoojoo Yun1,3, Jeongmin Park1, Joonggyu Kim1, Thuy Kieu Truong1, Jeong-Gyun Kim1, Nahee Park1, Hoyeol Yun2, Sang Wook Lee2, Young Hee Lee1 and Dongseok Suh1

Published 5 August 2015 • © 2015 IOP Publishing Ltd • Nanotechnology, Volume 26, Number 34

Abstract

The combination of quantum Hall conductance and charge-trap memory operation was qualitatively examined using a graphene field-effect transistor. The characteristics of two-terminal quantum Hall conductance appeared clearly on the background of a huge conductance hysteresis during a gate-voltage sweep for a device using monolayer graphene as a channel, hexagonal boron-nitride flakes as a tunneling dielectric and defective silicon oxide as the charge storage node. Even though there was a giant shift of the charge neutrality point, the deviation of quantized resistance value at the state of filling factor 2 was less than 1.6% from half of the von Klitzing constant. At high Landau level indices, the behaviors of quantum conductance oscillation between the increasing and the decreasing electron densities were identical in spite of a huge memory window exceeding 100 V. Our results indicate that the two physical phenomena, two-terminal quantum Hall conductance and charge-trap memory operation, can be integrated into one device without affecting each other.

https://iopscience.iop.org/article/10.1088/0957-4484/26/34/345202/pdf

A NIST paper on the Hall Effect:
---------

Developing a 'Gold Standard' for Hall Resistance

April 7, 2014

*
Contact: Rand Elmquist
(301) 975-6591

close-up of Hall bar and contacts

Configuration of the QHE device showing dimensions. The blue-gray rectangle in the center is the open face of the Hall bar. The locations of graphene components are outlined by white lines. Source and drain are at the left and right ends of the bar. There are electrical contacts above and below the bar. Click on image for enlarged view.
PML researchers have developed a novel method of fabricating graphene-based microdevices that may hasten the arrival of a new generation of standards for electrical resistance. The new design offers substantial performance enhancement over most existing devices, and can be adjusted to produce a wide range of electronic properties.

Since 1990, the internationally accepted means of realizing the ohm has been based on the quantum Hall effect* (QHE), in which resistance is exactly quantized in increments dictated by constants of nature. The QHE is measured using electrical contacts placed along the sides of a rectangular, cryogenically cooled, current-bearing conductor (the “Hall bar”) in which the charge carriers behave like a two-dimensional (2D) gas.

Charge carriers then condense at one or more energy levels in a strong magnetic field, and this produces resistance plateaus. The widely-used standards for such measurements are based on GaAs/AlGaAs heterostructure devices and require high magnetic field strengths in the range of 5 tesla (T) to 15 T, typically obtainable only with expensive superconducting magnets.

When QHE was first observed in graphene ten years ago, the inherently 2D material became a prime candidate for realizing the quantized Hall resistance (QHR) standard because QHE plateaus could be observed in graphene at lower magnetic field strength and higher temperature than in semiconductor devices.

In general, there are three ways to obtain monolayer graphene sheets suitable to that task: the sticky-tape “exfoliation” method used in 2004 to isolate the material for the first time; chemical vapor deposition on copper or other material; and growth on an insulating silicon carbide substrate, which the PML researchers employ.**

No matter how it is obtained, however, incorporating graphene into a practical standard entails the same sort of lithographic techniques used to fabricate most microstructures: features are created by spin-coating a polymer-based liquid over a surface, drying it, and exposing certain regions of the sample to light or to an electron beam to form masks for etching.

“There are serious difficulties when working on graphene in that environment,” says physicist Rand Elmquist of the Quantum Measurement Division. “Being an open surface, graphene is very sensitive to chemicals in the air or from materials it contacts. In normal photolithography or electron-beam lithography, the fabrication process lays down organic compounds – the liquid resist – onto whatever material is being treated. Those organic compounds leave a residue on graphene that won’t come off, creating imperfections in surfaces and contacts that can affect the electronic behavior.

“So we came up with a new way to make devices that we hoped would produce better contacts, and also keep the graphene clean, and free of organic contamination.”

This method, developed at PML by physicist Yanfei Yang involves coating a sheet of graphene on a section of silicon carbide wafer with about 15 nanometers of gold before any lithography. Patterns are developed using traditional photolithography to remove any unwanted gold-coated graphene. Then, the areas that will be the Hall bar contacts get a thicker coating of gold, so that they will make good connections for wires used in electrical measurements. In the last step, the gold layer over the area of graphene that will serve as the Hall bar is removed with dilute aqua regia, a mixture of nitric acid, hydrochloric acid, and deionized water, leaving the graphene almost completely clean.



“To our surprise,” says Elmquist of the Fundamental Electrical Measurements Group, “we found that aqua regia etching produces helpful p-type doping in the graphene.” That is, molecules from the acids stick to the surface, reducing the carrier density and improving the mobility of electrons that remain. Low carrier density is important because the higher the density of charge-carriers in the Hall bar, the higher the magnetic field strength required to observe the critical QHE plateaus.

“Normal epitaxial graphene (EG) grown on SiC has an electron density of 1013 per square centimeter,” Elmquist says. “At that level, you can’t see the QHE”; doing so would require a magnetic field strength far too high to be used in a working standard. “As a practical matter, you need to get down to around 5 x 1011 per cm2 or lower for use at reasonable field strength.”

By contrast, the PML group’s new EG devices were shown to have carrier densities in the range of 3 x 1010 per cm2 to 3 x 1011 per cm2, allowing observation of clearly defined resistance quantization at magnetic field strengths of less than 4 T. The p-type molecular doping effect can be reduced by heating in argon gas, and is restored by dipping in aqua regia.

The team has submitted its results for publication in the journal Advanced Materials. But there is much more to learn. “One thing we are working on is a better understanding of how the QHE develops in graphene, and specific features of the QHE that occur nowhere else” Elmquist says; “One day soon we hope to implement this or a similar method to make nearly perfect graphene QHR devices that surpass the best grown with GaAs.”

* The Hall effect occurs when current traveling through a conductor is exposed to a magnetic field oriented at a 90-degree angle to the current flow. Because of the effect of the field on the charge carriers, electron (or hole) populations are higher on one side of the conductor and lower on the other. This produces a transverse voltage that is perpendicular to both the current flow and the field. At the quantum level, the effect is exactly quantized, and resistance – as determined by the ratio of transverse voltage to current – is thus also quantized.

** The PML group makes epitaxial graphene (EG) by heating a crystal of SiC to as high as 2100 ͦC. Silicon on the outermost surface turns to gas. The remaining carbon atoms arrange themselves into hexagonal units and form a sheet of graphene atop and aligned with the underlying crystal. The EG process has advantages for making devices compared to the other two familiar sources of graphene. Exfoliation of graphite produces sheets with dimensions in the range of tens of micrometers – too small for many uses. And graphene grown by chemical vapor deposition has to be removed from its metal substrate and transferred elsewhere, whereas EG can be used as formed. One drawback to the technique is that the EG layers are doped by the formation of covalent bonds with the underlying crystal and have high electron densities.

The collaboration includes researchers now at Georgetown University and institutions in Japan, Taiwan, and Argentina.

You have managed to perform a monumental research effort here, Cr6. Every time I read these posts I want to get in and model something but I am tied into other projects at the moment and can't really fit another one in. Very interesting stuff.

Nevyn wrote:You have managed to perform a monumental research effort here, Cr6. Every time I read these posts I want to get in and model something but I am tied into other projects at the moment and can't really fit another one in. Very interesting stuff.

Thanks Nevyn,

I just found these articles of interest around graphene's diverse properties. I kind of figure that Mathis' work will eventually provide the most comprehensive explanation.  Your work is fantastic on the viewers.  Just really cool and interesting. I understand priorities in development so go with what you see as the most necessary.  I kind of figured that graphene is going to get "huge" attention in the nano-tech world in the future.  It is best we see it from a Mathis' point of view.

Here's an article on Graphene and "spasers" and "Plasmons" (I bet Mathis could provide us with some clues on this eventually)... it looks like a pretty promising approach to cancer treatments:
--------
Death Ray 'Spasers' Kill Cancer
Nov 4, 2014 01:00 PM ET // by Neil Savage, IEEE Spectrum
http://spectrum.ieee.org/

http://news.discovery.com/tech/nanotechnology/death-ray-spasers-kill-cancer-141104.htm

Encircling tumors with a phalanx of miniature lasers could offer a new way to battle cancer, a team of Australian researchers is proposing.

Technically, the proposed device isn’t really a laser at all, but a spaser, with surface plasmons rather than light undergoing amplification.
How Nanotech Can Make A Better You: Photos

Plasmons are oscillations in electron density created in the surface of a small metal object when photons strike it. It’s possible to design a device so that the plasmons feed back on themselves, amplifying in much the same way photons bouncing around a laser cavity stimulate the emission of other photons, creating laser light.

“The spaser is basically the same as a laser,” says Chanaka Rupasinghe, a postgraduate student in electrical and computer engineering at Monash University near Melbourne, Australia. He and his professor, Malin Premaratne, presented their idea in a paper at the recent IEEE Photonics Conference, in Los Angeles.

Spasers have been built of gold nanoparticles surrounded by a silica shell and from cadmium sulfide nanowires on a silver substrate. Earlier this year, Rupasinghe and Premaratne proposed a different design, using graphene and carbon nanotubes.

In their setup, a carbon nanotube would absorb the energy from a separate laser source and transfer it to the surface plasmons of a nearby nanoflake of graphene, creating the spaser effect. Pumping the spaser with 1200-nanometer light would cause it to output light at 1700 nm, Rupasinghe says. They argued their spaser would be mechanically strong but flexible, chemically and thermally stable, and compatible with biomedical applications.

Once they had their design, their next idea was to use it to replace some of the nanoparticles already being explored as cancer treatments that are being designed to deliver drugs directly to tumors. The nanotubes and graphene flakes could have antibodies or ligands attached to them that would draw them to the tumor. Once at the tumor, they’d self-assemble into an array of spasers.

“You surround cancer cells with very tiny lasers, instead of nanoparticles,” Rupasinghe says.
Can Bras Cause Cancer?

An external laser producing light between 1000 and 1350 nm could penetrate several centimeters of human tissue and act as a power source for the spaser array. The spasers would then deliver a concentrated blast of heat to the cancer cells. At the same time, Rupasinghe says, the nanotubes could be designed to carry drugs to their target, hitting the tumor with a one-two punch.

No one has yet built the graphene-nanotube spasers, let alone started the long process to see whether they’d make a safe and effective cancer treatment. “Our team is basically a theoretical and modelling group,” Rupasinghe says. But his hope is that this idea may someday provide another weapon in the anti-tumor arsenal.

Get more from IEEE Spectrum

This article originally appeared on IEEE Spectrum; all rights reserved.

http://news.discovery.com/tech/nanotechnology/death-ray-spasers-kill-cancer-141104.htm
----------


Graphene- carbon nanotube spaser nanolaser introduced
We have been able to design the world's first 'spaser' - a nanoscale laser - made out of graphene and carbon. A spaser (surface plasmon amplication by stimulated emission of radiation) is effectively a nanoscale laser, or a nanonlaser. It has been touted as the future of optical computers and technologies. It could enable ‘nanophotonic’ circuitry, extremely small circuits far tinier than anything available today. This could usher in many technological advances including microchips hundred times more powerful than anything we have today.

'Our device would be comprised of a graphene resonator and a carbon nanotube gain element.'

'The use of carbon means our spaser would be more robust and flexible, would operate at high temperatures, and be eco-friendly'

See dailymail.co.uk article for more information
http://www.dailymail.co.uk/sciencetech/article-2614883/Your-T-shirt-ringing-Mobile-phones-soon-built-CLOTHES-thanks-breakthrough-tiny-microchips.html
http://www.chanakarupasinghe.com/

'Simple, green, and cost-effective' method of graphene production announced

   Ben Coxworth
   June 21, 2011


http://www.gizmag.com/graphene-production-magnesium-dry-ice/18986/



Graphene, the one-atom-thick carbon sheet material that could revolution everything from energy storage to computer chips, can now be made much more easily - at least, that's what scientists from Northern Illinois University (NIU) are telling us. While previous production methods have included things like repeatedly splitting graphite crystals with tape, heating silicon carbide to high temperatures, and various other approaches, the latest process simply involves burning pure magnesium in dry ice.

The graphene created consists of several layers - not just one - although it is still less than ten atoms thick.

"It is scientifically proven that burning magnesium metal in carbon dioxide produces carbon, but the formation of this carbon with few-layer graphene as the major product has neither been identified nor proven as such until our current report," said Narayan Hosmane, an NIU professor of chemistry and biochemistry, and leader of the project. "The synthetic process can be used to potentially produce few-layer graphene in large quantities. Up until now, graphene has been synthesized by various methods utilizing hazardous chemicals and tedious techniques. This new method is simple, green and cost-effective."

Hosmane's team had set out to produce single-wall carbon nanotubes, and inadvertently discovered the graphene-production method in the process.

The research was recently published in the Journal of Materials Chemistry.

Last November, researchers from Rice University announced another promising graphene production method, that utilizes simple table sugar.

Journal of Physics: Condensed Matter

Graphene grown on magnesium oxide has a band gap

Can graphene/MgO heterojunctions be the basis for graphene transistors on Si(100)?

1.5 monolayer graphene film grown by PVD on MgO(111).

Graphene is an exciting electronic material due to extremely high room temperature mobilities. The lack of a band gap and the inability to grow graphene directly on dielectric substrates has hindered the development of practical graphene logic devices on Si. Graphene has now been grown by direct chemical and physical vapour deposition on MgO(111). Graphene/MgO interactions destroy the chemical equivalency of adjacent graphene sites, thus opening a band gap of around 0.5–1 eV. Since MgO(111) films have been grown on Si(100), a graphene/MgO/Si(100) transistor is a possibility.

The finding that electrons in graphene layers behave as massless fermions has opened broad new possibilities for truly disruptive, ultrafast graphene-based electronic devices. Two major obstacles, however, have blocked the development of practical graphene devices integrated with Si CMOS: (a) the inability to grow graphene layers on dielectric substrates by practical, scalable methods, such as chemical or physical vapor deposition, and (b) the absence of a graphene band gap, which hinders logic device applications. New work has demonstrated that graphene films can be deposited by chemical or physical vapor deposition (CVD, PVD) on MgO(111), and that a 2.5 monolayer-thick graphene film on MgO(111) displays a band gap, suitable for logic applications.

In recent work published in J. Phys.: Condens. Matter 23 072204, the low energy electron diffraction (LEED) intensities of graphene films deposited by CVD or PVD were analyzed, and shown to display three-fold, rather than six-fold symmetry. The data demonstrate that adjacent atoms on the graphene lattice are no longer chemically equivalent, thus lifting the highest occupied/lowest unoccupied molecular orbital (HOMO/LUMO) degeneracy at the Dirac point and opening a band gap. The data also strongly suggest that the size of the band gap decreases with an increasing number of graphene layers. While the electron transport characteristics of graphene films on MgO have yet to be determined, the ability to systematically vary the number of graphene layers should permit 'tuning' of band gap and charge transport properties. Since the growth of MgO(111) films on Si(100) has been reported, there now exists a potential direct route towards the formation of graphene transistors on Si(100).

https://iopscience.iop.org/0953-8984/labtalk-article/45265

Graphene Effectively Filters Electrons According to the Direction of Their Spin
December 26, 2013

New research from MIT shows that graphene can effectively filter electrons according to the direction of their spin, something that cannot be done by any conventional electronic system.

Graphene has become an all-purpose wonder material, spurring armies of researchers to explore new possibilities for this two-dimensional lattice of pure carbon. But new research at MIT has found additional potential for the material by uncovering unexpected features that show up under some extreme conditions — features that could render graphene suitable for exotic uses such as quantum computing.

The research is published this week in the journal Nature, in a paper by professors Pablo Jarillo-Herrero and Ray Ashoori, postdocs Andrea Young and Ben Hunt, graduate student Javier Sanchez-Yamaguchi, and three others. Under an extremely powerful magnetic field and at extremely low temperature, the researchers found, graphene can effectively filter electrons according to the direction of their spin, something that cannot be done by any conventional electronic system.

Under typical conditions, sheets of graphene behave as normal conductors: Apply a voltage, and current flows throughout the two-dimensional flake. If you turn on a magnetic field perpendicular to the graphene flake, however, the behavior changes: Current flows only along the edge, while the bulk remains insulating. Moreover, this current flows only in one direction — clockwise or counterclockwise, depending on the orientation of the magnetic field — in a phenomenon known as the quantum Hall effect.

In the new work, the researchers found that if they applied a second powerful magnetic field — this time in the same plane as the graphene flake — the material’s behavior changes yet again: Electrons can move around the conducting edge in either direction, with electrons that have one kind of spin moving clockwise while those with the opposite spin move counterclockwise.

“We created an unusual kind of conductor along the edge,” says Young, a Pappalardo Postdoctoral Fellow in MIT’s physics department and the paper’s lead author, “virtually a one-dimensional wire.” The segregation of electrons according to spin is “a normal feature of topological insulators,” he says, “but graphene is not normally a topological insulator. We’re getting the same effect in a very different material system.”

What’s more, by varying the magnetic field, “we can turn these edge states on and off,” Young says. That switching capability means that, in principle, “we can make circuits and transistors out of these,” he says, which has not been realized before in conventional topological insulators.

There is another benefit of this spin selectivity, Young says: It prevents a phenomenon called “backscattering,” which could disrupt the motion of the electrons. As a result, imperfections that would ordinarily ruin the electronic properties of the material have little effect. “Even if the edges are ‘dirty,’ electrons are transmitted along this edge nearly perfectly,” he says.

Jarillo-Herrero, the Mitsui Career Development Associate Professor of Physics at MIT, says the behavior seen in these graphene flakes was predicted, but never seen before. This work, he says, is the first time such spin-selective behavior has been demonstrated in a single sheet of graphene, and also the first time anyone has demonstrated the ability “to transition between these two regimes.”

That could ultimately lead to a novel way of making a kind of quantum computer, Jarillo-Herrero says, something that researchers have tried to do, without success, for decades. But because of the extreme conditions required, Young says, “this would be a very specialized machine” used only for high-priority computational tasks, such as in national laboratories.

Ashoori, a professor of physics, points out that the newly discovered edge states have a number of surprising properties. For example, although gold is an exceptionally good electrical conductor, when dabs of gold are added to the edge of the graphene flakes, they cause the electrical resistance to increase. The gold dabs allow the electrons to backscatter into the oppositely traveling state by mixing the electron spins; the more gold is added, the more the resistance goes up.

This research represents “a new direction” in topological insulators, Young says. “We don’t really know what it might lead to, but it opens our thinking about the kind of electrical devices we can make.”

The experiments required the use of a magnetic field with a strength of 35 tesla — “about 10 times more than in an MRI machine,” Jarillo-Herrero says — and a temperature of just 0.3 degrees Celsius above absolute zero. However, the team is already pursuing ways of observing a similar effect at magnetic fields of just one tesla — similar to a strong kitchen magnet — and at higher temperatures.

(More at link:
http://scitechdaily.com/graphene-effectively-filters-electrons-according-direction-spin/
)

Could ‘miracle’ material graphene finally have a use by making seawater drinkable?

Published time: 4 Apr, 2017 15:52

Water, water everywhere, but not a drop to drink? The Rime of the Ancient Mariner may soon be left redundant now that scientists have devised a sieve made of ‘miracle material’ graphene capable of removing salt molecules from seawater, rendering it safe to drink.

When it was discovered by Andre Geim and his colleague Konstantin Novoselov, physics professors working at Manchester University around 2004, graphene was hailed as a ground-breaking discovery, with the media calling it a “wonder material.”
...more at link

Nair stressed the importance of the pores being just the right size to capture the salt molecules while releasing the water ones.

“To make it permeable, you need to drill small holes in the membrane.

“But if the hole size is larger than one nanometre, the salts go through that hole.

“You have to make a membrane with a very uniform less-than-one-nanometre hole size to make it useful for desalination.

“It is a really challenging job,” he added.

The graphene oxide membrane previously showed signs of swelling when dipped into water, meaning smaller salts could still permeate. By adding walls of epoxy resin on either side of the membrane, however, scientists found they could stop the pores expanding.

“This is our first demonstration that we can control the spacing [of pores in the membrane] and that we can do desalination, which was not possible before.

“The next step is to compare this with the state-of-the-art material available on the market.”

Up to 14 percent of the world’s population will struggle with water supply by 2025, according to the United Nations. WaterAid claims one in 10 people already live without safe water.

As climate change takes its toll, more countries are likely to consider investing in desalination technologies.

Desalination plants currently use polymer-based membranes. However, it is hoped that graphene oxide will prove more efficient, scaling up water distillation around the world, especially in poor regions where such facilities are prohibitively expensive.

Following news of the ground-breaking research, Ram Devanathan, from the Pacific Northwest National Laboratory in Richland, US, said more work needs to be done to produce the membranes inexpensively on an industrial scale.

Writing in the Nature Nanotechnology science journal, Devanathan said: “The selective separation of water molecules from ions by physical restriction of interlayer spacing opens the door to the synthesis of inexpensive membranes for desalination.”

https://www.rt.com/uk/383480-graphene-sieve-drinking-water/
related:
Out of thin air: Scientists create solar powered device turning air into drinking water
Published time: 16 Apr, 2017 04:05
https://www.rt.com/viral/384909-air-water-solar-power/

Graphene 'copy machine' may produce cheap semiconductor wafers
Engineers use graphene as a 'copy machine' to produce cheaper semiconductor wafers

(more at link...)

Date: April 19, 2017
Source: Massachusetts Institute of Technology
Summary:
A new technique may vastly reduce the overall cost of wafer technology and enable devices made from more exotic, higher-performing semiconductor materials than conventional silicon. The new method uses graphene -- single-atom-thin sheets of graphite -- as a sort of 'copy machine' to transfer intricate crystalline patterns from an underlying semiconductor wafer to a top layer of identical material.

n 2016, annual global semiconductor sales reached their highest-ever point, at $339 billion worldwide. In that same year, the semiconductor industry spent about $7.2 billion worldwide on wafers that serve as the substrates for microelectronics components, which can be turned into transistors, light-emitting diodes, and other electronic and photonic devices.

A new technique developed by MIT engineers may vastly reduce the overall cost of wafer technology and enable devices made from more exotic, higher-performing semiconductor materials than conventional silicon.

The new method, reported in Nature, uses graphene -- single-atom-thin sheets of graphite -- as a sort of "copy machine" to transfer intricate crystalline patterns from an underlying semiconductor wafer to a top layer of identical material.

The engineers worked out carefully controlled procedures to place single sheets of graphene onto an expensive wafer. They then grew semiconducting material over the graphene layer. They found that graphene is thin enough to appear electrically invisible, allowing the top layer to see through the graphene to the underlying crystalline wafer, imprinting its patterns without being influenced by the graphene.

Graphene is also rather "slippery" and does not tend to stick to other materials easily, enabling the engineers to simply peel the top semiconducting layer from the wafer after its structures have been imprinted.

Jeehwan Kim, the Class of 1947 Career Development Assistant Professor in the departments of Mechanical Engineering and Materials Science and Engineering, says that in conventional semiconductor manufacturing, the wafer, once its crystalline pattern is transferred, is so strongly bonded to the semiconductor that it is almost impossible to separate without damaging both layers.

"You end up having to sacrifice the wafer -- it becomes part of the device," Kim says.

With the group's new technique, Kim says manufacturers can now use graphene as an intermediate layer, allowing them to copy and paste the wafer, separate a copied film from the wafer, and reuse the wafer many times over. In addition to saving on the cost of wafers, Kim says this opens opportunities for exploring more exotic semiconductor materials.

"The industry has been stuck on silicon, and even though we've known about better performing semiconductors, we haven't been able to use them, because of their cost," Kim says. "This gives the industry freedom in choosing semiconductor materials by performance and not cost."

Kim's research team discovered this new technique at MIT's Research Laboratory of Electronics. Kim's MIT co-authors are first author and graduate student Yunjo Kim; graduate students Samuel Cruz, Babatunde Alawonde, Chris Heidelberger, Yi Song, and Kuan Qiao; postdocs Kyusang Lee, Shinhyun Choi, and Wei Kong; visiting research scholar Chanyeol Choi; Merton C. Flemings-SMA Professor of Materials Science and Engineering Eugene Fitzgerald; professor of electrical engineering and computer science Jing Kong; and assistant professor of mechanical engineering Alexie Kolpak; along with Jared Johnson and Jinwoo Hwang from Ohio State University, and Ibraheem Almansouri of Masdar Institute of Science and Technology.

Graphene shift

Since graphene's discovery in 2004, researchers have been investigating its exceptional electrical properties in hopes of improving the performance and cost of electronic devices. Graphene is an extremely good conductor of electricity, as electrons flow through graphene with virtually no friction. Researchers, therefore, have been intent on finding ways to adapt graphene as a cheap, high-performance semiconducting material.

"People were so hopeful that we might make really fast electronic devices from graphene," Kim says. "But it turns out it's really hard to make a good graphene transistor."

In order for a transistor to work, it must be able to turn a flow of electrons on and off, to generate a pattern of ones and zeros, instructing a device on how to carry out a set of computations. As it happens, it is very hard to stop the flow of electrons through graphene, making it an excellent conductor but a poor semiconductor.

Kim's group took an entirely new approach to using graphene in semiconductors. Instead of focusing on graphene's electrical properties, the researchers looked at the material's mechanical features.

"We've had a strong belief in graphene, because it is a very robust, ultrathin, material and forms very strong covalent bonding between its atoms in the horizontal direction," Kim says. "Interestingly, it has very weak Van der Waals forces, meaning it doesn't react with anything vertically, which makes graphene's surface very slippery."

Copy and peel

The team now reports that graphene, with its ultrathin, Teflon-like properties, can be sandwiched between a wafer and its semiconducting layer, providing a barely perceptible, nonstick surface through which the semiconducting material's atoms can still rearrange in the pattern of the wafer's crystals. The material, once imprinted, can simply be peeled off from the graphene surface, allowing manufacturers to reuse the original wafer.

The team found that its technique, which they term "remote epitaxy," was successful in copying and peeling off layers of semiconductors from the same semiconductor wafers. The researchers had success in applying their technique to exotic wafer and semiconducting materials, including indium phosphide, gallium arsenenide, and gallium phosphide -- materials that are 50 to 100 times more expensive than silicon.

Kim says that this new technique makes it possible for manufacturers to reuse wafers -- of silicon and higher-performing materials -- "conceptually, ad infinitum."

An exotic future

The group's graphene-based peel-off technique may also advance the field of flexible electronics. In general, wafers are very rigid, making the devices they are fused to similarly inflexible. Kim says now, semiconductor devices such as LEDs and solar cells can be made to bend and twist. In fact, the group demonstrated this possibility by fabricating a flexible LED display, patterned in the MIT logo, using their technique.

"Let's say you want to install solar cells on your car, which is not completely flat -- the body has curves," Kim says. "Can you coat your semiconductor on top of it? It's impossible now, because it sticks to the thick wafer. Now, we can peel off, bend, and you can do conformal coating on cars, and even clothing."

Going forward, the researchers plan to design a reusable "mother wafer" with regions made from different exotic materials. Using graphene as an intermediary, they hope to create multifunctional, high-performance devices. They are also investigating mixing and matching various semiconductors and stacking them up as a multimaterial structure.
...

Story Source:

Materials provided by Massachusetts Institute of Technology. Original written by Jennifer Chu. Note: Content may be edited for style and length.

Journal Reference:

Yunjo Kim, Samuel S. Cruz, Kyusang Lee, Babatunde O. Alawode, Chanyeol Choi, Yi Song, Jared M. Johnson, Christopher Heidelberger, Wei Kong, Shinhyun Choi, Kuan Qiao, Ibraheem Almansouri, Eugene A. Fitzgerald, Jing Kong, Alexie M. Kolpak, Jinwoo Hwang, Jeehwan Kim. Remote epitaxy through graphene enables two-dimensional material-based layer transfer. Nature, 2017; 544 (7650): 340 DOI: 10.1038/nature22053

Laser 3D printing helps Rice, Tianjin researchers create atomically thin graphene

Jun 21, 2017 | By Benedict

Nanotechnologists from Rice University and China’s Tianjin University have used laser 3D printing to fabricate centimeter-sized objects of atomically thin graphene. The research could help create industrial quantities of bulk graphene.

Nickel functions as a catalyst to turn laser-melted sugar into graphene

It’s hardly surprising that graphene, a two-dimensional sheet of pure carbon, is a subject of great interest for materials scientists. Not only is graphene incredibly strong, it’s also conductive, and can therefore be used in a wide range of applications, from nanoelectronics to bone implants.

The challenge is getting reasonably sized quantities of 3D graphene. To do the most useful stuff with the material, bulk quantities are needed, and scientists have so far had trouble making graphene on that scale in an efficient way.

A team of nanotechnologists from Rice University and China’s Tianjin University recently used 3D laser printing to fabricate centimeter-sized objects of atomically thin graphene, in a research project that could someday lead to the simple fabrication of bulk quantities of graphene from non-graphene starting materials.

For the research project, the laboratory of Rice chemist James Tour joined forces with the labs of Rice’s Jun Luo and Tianjin’s Naiqin Zhao to adapt a common 3D printing technique. The technique, conducted at room temperature, was used to make fingertip-size blocks of graphene foam. No molds were required, and the starting materials consisted of just powdered sugar and nickel powder.

3D printing was used to produce a porous graphene foam

“This simple and efficient method does away with the need for both cold-press molds and high-temperature CVD treatment,” said co-lead author Junwei Sha, a former student in Tour’s lab and current postdoctoral researcher at Tianjin.

“We should also be able to use this process to produce specific types of graphene foam like 3D printed rebar graphene as well as both nitrogen- and sulfur-doped graphene foam by changing the precursor powders.”

To create their blocks of graphene, the researchers used a CO2 laser—the kind used by laser sintering 3D printers. When the laser was shone onto the sugar and nickel powder, the sugar was melted and the nickel acted as a catalyst. A low-density graphene with large pores then formed as the mixture cooled down. (These pores accounted for 99 percent of the material’s volume.)

This laser shining process was repeated over and over again with different parameters, as the researchers sought to find the optimal amount of time and laser power that would maximize graphene production.

James Tour, the T.T. and W.F. Chao Chair in Chemistry at Rice University

Having settled on an effective combination of parameters, the researchers believe that their technique could have many uses across different fields.

“The 3D graphene foams prepared by our method show promise for applications that require rapid prototyping and manufacturing of 3D carbon materials, including energy storage, damping, and sound absorption,” said co-lead author Yilun Li, a graduate student at Rice.

http://www.3ders.org/articles/20170621-laser-3d-printing-helps-rice-tianjin-researchers-create-atomically-thin-graphene.html

Nokia patents graphene-based flexible photon battery

Nokia has recently issued what could be a truly revolutional patent: a self-charging graphene-based photon battery, capable of being printed on flexible substrates.

https://www.graphene-info.com/nokia-patents-graphene-based-flexible-photon-battery

The patent describes a battery that can regenerate itself immediately after discharge through continuous chemical reactions, without an external energy input. The result is an energy autonomous device. The battery uses humid air for the purpose of recharging and be made highly transparent.

Whether this patent will actually be used for the manufacturing of commercial devices remains to be seen, but if it does, it should be quite life-changing.

https://www.graphene-info.com/nokia-patents-graphene-based-flexible-photon-battery
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This site has a Graphene Handbook (Mertens) for sale $97 covering these topics. It was recent publication. I'm sure at some point he will have to have a Chapter on "Mathis"
https://www.graphene-info.com/img/services/graphene-handbook/graphene-contents-layout.jpg

Found this on the "Microwave" method with a close up of Graphene.
(more at link...)
https://phys.org/news/2016-09-microwaves-high-quality-graphene.html
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Researchers use microwaves to produce high-quality graphene
September 1, 2016, Rutgers University
Rutgers engineers use microwaves to produce high-quality graphene
Scanning electron microscopy imagery of a graphene fiber made from microwave reduced graphene oxide. Credit: Jieun Yang, Damien Voiry and Jacob Kupferberg

Rutgers University engineers have found a simple method for producing high-quality graphene that can be used in next-generation electronic and energy devices: bake the compound in a microwave oven.

The discovery is documented in a study published online today in the journal Science.

"This is a major advance in the graphene field," said Manish Chhowalla, professor and associate chair in the Department of Materials Science and Engineering in Rutgers' School of Engineering. "This simple microwave treatment leads to exceptionally high quality graphene with properties approaching those in pristine graphene."

The discovery was made by post-doctoral associates and undergraduate students in the department, said Chhowalla, who is also the director of the Rutgers Institute for Advanced Materials, Devices and Nanotechnology. Having undergraduates as co-authors of a Science paper is rare but he said "the Rutgers Materials Science and Engineering Department and the School of Engineering at Rutgers cultivate a culture of curiosity driven research in students with fresh ideas who are not afraid to try something new.''

Graphene - 100 times tougher than steel - conducts electricity better than copper and rapidly dissipates heat, making it useful for many applications. Large-scale production of graphene is necessary for applications such as printable electronics, electrodes for batteries and catalysts for fuel cells.

Just wanted to add these links to Miles' new paper on Graphene and our humble contributions:

http://milesmathis.com/graphene.pdf
https://milesmathis.forumotion.com/t409-new-paper-on-graphene

Here's a mainstream definition:
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Graphene Structure

Graphene is, basically, a single atomic layer of graphite; an abundant mineral which is an allotrope of carbon that is made up of very tightly bonded carbon atoms organised into a hexagonal lattice. What makes graphene so special is its sp2 hybridisation and very thin atomic thickness (of 0.345Nm). These properties are what enable graphene to break so many records in terms of strength, electricity and heat conduction (as well as many others). Now, let’s explore just what makes graphene so special, what are its intrinsic properties that separate it from other forms of carbon, and other 2D crystalline compounds?
Fundamental Characteristics

Before monolayer graphene was isolated in 2004, it was theoretically believed that two dimensional compounds could not exist due to thermal instability when separated. However, once graphene was isolated, it was clear that it was actually possible, and it took scientists some time to find out exactly how. After suspended graphene sheets were studied by transmission electron microscopy, scientists believed that they found the reason to be due to slight rippling in the graphene, modifying the structure of the material. However, later research suggests that it is actually due to the fact that the carbon to carbon bonds in graphene are so small and strong that they prevent thermal fluctuations from destabilizing it.

Electronic Properties

One of the most useful properties of graphene is that it is a zero-overlap semimetal (with both holes and electrons as charge carriers) with very high electrical conductivity. Carbon atoms have a total of 6 electrons; 2 in the inner shell and 4 in the outer shell. The 4 outer shell electrons in an individual carbon atom are available for chemical bonding, but in graphene, each atom is connected to 3 other carbon atoms on the two dimensional plane, leaving 1 electron freely available in the third dimension for electronic conduction. These highly-mobile electrons are called pi (π) electrons and are located above and below the graphene sheet. These pi orbitals overlap and help to enhance the carbon to carbon bonds in graphene. Fundamentally, the electronic properties of graphene are dictated by the bonding and anti-bonding (the valance and conduction bands) of these pi orbitals.

Combined research over the last 50 years has proved that at the Dirac point in graphene, electrons and holes have zero effective mass. This occurs because the energy – movement relation (the spectrum for excitations) is linear for low energies near the 6 individual corners of the Brillouin zone. These electrons and holes are known as Dirac fermions, or Graphinos, and the 6 corners of the Brillouin zone are known as the Dirac points. Due to the zero density of states at the Dirac points, electronic conductivity is actually quite low. However, the Fermi level can be changed by doping (with electrons or holes) to create a material that is potentially better at conducting electricity than, for example, copper at room temperature.

Tests have shown that the electronic mobility of graphene is very high, with previously reported results above 15,000 cm2·V−1·s−1 and theoretically potential limits of 200,000 cm2·V−1·s−1 (limited by the scattering of graphene’s acoustic photons). It is said that graphene electrons act very much like photons in their mobility due to their lack of mass. These charge carriers are able to travel sub-micrometer distances without scattering; a phenomenon known as ballistic transport. However, the quality of the graphene and the substrate that is used will be the limiting factors. With silicon dioxide as the substrate, for example, mobility is potentially limited to 40,000 cm2·V−1·s−1.

"In terms of how far along we are to understanding the true properties of graphene, this is just the tip of iceberg. Before graphene is heavily integrated into the areas in which we believe it will excel at, we need to spend a lot more time understanding just what makes it such an amazing material"

Mechanical Strength

Another of graphene’s stand-out properties is its inherent strength. Due to the strength of its 0.142 Nm-long carbon bonds, graphene is the strongest material ever discovered, with an ultimate tensile strength of 130,000,000,000 Pascals (or 130 gigapascals), compared to 400,000,000 for A36 structural steel, or 375,700,000 for Aramid (Kevlar). Not only is graphene extraordinarily strong, it is also very light at 0.77milligrams per square metre (for comparison purposes, 1 square metre of paper is roughly 1000 times heavier). It is often said that a single sheet of graphene (being only 1 atom thick), sufficient in size enough to cover a whole football field, would weigh under 1 single gram.

What makes this particularly special is that graphene also contains elastic properties, being able to retain its initial size after strain. In 2007, Atomic force microscopic (AFM) tests were carried out on graphene sheets that were suspended over silicone dioxide cavities. These tests showed that graphene sheets (with thicknesses of between 2 and 8 Nm) had spring constants in the region of 1-5 N/m and a Young’s modulus (different to that of three-dimensional graphite) of 0.5 TPa. Again, these superlative figures are based on theoretical prospects using graphene that is unflawed containing no imperfections whatsoever and currently very expensive and difficult to artificially reproduce, though production techniques are steadily improving, ultimately reducing costs and complexity.

Optical Properties

Graphene’s ability to absorb a rather large 2.3% of white light is also a unique and interesting property, especially considering that it is only 1 atom thick. This is due to its aforementioned electronic properties; the electrons acting like massless charge carriers with very high mobility. A few years ago, it was proved that the amount of white light absorbed is based on the Fine Structure Constant, rather than being dictated by material specifics. Adding another layer of graphene increases the amount of white light absorbed by approximately the same value (2.3%). Graphene’s opacity of πα ≈ 2.3% equates to a universal dynamic conductivity value of G=e2/4ℏ (±2-3%) over the visible frequency range.

Due to these impressive characteristics, it has been observed that once optical intensity reaches a certain threshold (known as the saturation fluence) saturable absorption takes place (very high intensity light causes a reduction in absorption). This is an important characteristic with regards to the mode-locking of fibre lasers. Due to graphene’s properties of wavelength-insensitive ultrafast saturable absorption, full-band mode locking has been achieved using an erbium-doped dissipative soliton fibre laser capable of obtaining wavelength tuning as large as 30 nm.
(more at link...)

https://www.graphenea.com/pages/properties-of-graphene

Miles hints at the male/female charge field bonding. I figured the alignment of these couplings may be at play? Looks like Japanese researchers found something matching with Mathis' description:

http://milesmathis.com/graphene.pdf
( page 6)
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Therefore, what we have is a proton and a neutron adjacent at the north pole of the nucleus, releasing
charge into this ambient field. And that field is spun opposite to the proton and neutron. Not only are
they releasing anticharge into a charge wind, which will tamp it down, they are releasing into a charge
wind that is tamping down their own greater spin. Yes, the proton and the neutron are also spinning.
Problem is, the proton and neutron won't respond to this strange situation in the same way. Since they
have different magnetic moments, they aren't spinning the same or releasing the same amount of
charge. Also remember that the neutron and proton are plugged in 90 degrees to one another. So in
effect we are backflushing the proton and neutron with the same current, but they are releasing this
current into an opposite field—a field they respond to differently. This differing response will cause
them to move apart, taking different angles to the field. Since the proton still determines the main line
of current, that is the current we will measure. But I predict a secondary line of current here, released
by the neutron. It may rejoin the current released by the proton, but close to the nucleus, there should
be two anticharge streams at the north pole.

This greater analysis also explains the magnetism of Graphene under an applied current. Since the
applied current is opposite to the charge direction of the Graphene itself, we would expect a tamping
down of the E field and a spinning up of the B field. See my paper on Period 4 and my analysis of Iron
for more on this. In short, when charge or anticharge predominates, you get an increase in E.
Electrical current is through charge in one direction. But when you have both charge and anticharge in
nearly equal amounts, one spins up the other, and you have an increase in magnetism at the atomic
level.

This also explains the spontaneous n-doping of Graphene on soda-lime glass. Depending on the
stability of the Graphene, it can take charge from either direction, but as we have seen it prefers anticharge.
Charge is what built it so charge is what will soon break it, applied with too much strength.
But the hanging bond at the north pole allows for an easy application of anticharge. Anticharge would
be a danger to Graphene only if it were so strong it completely overwhelmed the main charge lines.

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Researchers have fabricated two types of trilayer graphene with different electrical properties
February 12, 2018, Tohoku University

https://phys.org/news/2018-02-fabricated-trilayer-graphene-electrical-properties.html

Graphene's carbon atoms are arranged into hexagons, forming a honeycomb-like lattice. Placing one layer of graphene on top of another leads to the formation of bilayer graphene. The layers can be arranged in one of two positions: the centres of the carbon hexagons of each layer can be organized immediately above one another, called AA-stacking, or they can be displaced forwards so that a hexagon centre in one layer is above a carbon atom below it, called AB-stacking. AB-stacking of two layers of graphene leads to the formation of a material with semiconducting properties by applying an external electric field.

Deliberately stacking three layers of graphene has proven difficult. But doing so could help researchers study how the physical properties of tri-layered materials change based on stacking orientation. This could lead to the development of novel electrical devices. Researchers at Japan's Tohoku University and Nagoya University have now fabricated two different types of trilayer graphene with different electrical properties.

They heated silicon carbide using one of two methods. In one experiment, silicon carbide was heated to 1,510°C under pressurized argon. In another, it was heated to 1,300°C in a high vacuum. Both materials were then sprayed with hydrogen gas in which the bonds were broken to form single hydrogen atoms. Two types of trilayer graphene then formed. The silicon carbide heated under pressurized argon formed into ABA-stacked graphene, in which the hexagons of the top and bottom layers were exactly aligned while the middle layer was slightly displaced. The silicon carbide heated in a vacuum developed into ABC-stacked graphene, in which each layer was slightly displaced in front of the one below it.

The researchers then examined the physical properties of each material and found that their electrons behaved differently. The ABA graphene was an excellent electrical conductor, similar to monolayer graphene. The ABC graphene, on the other hand, acts more like AB graphene in that it had semi-conductor properties.

This came out recently...might need to review Miles' paper one more time to see if the charge field aligns differently with a "twist":
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(more at link....)

Give double-layer graphene a twist and it superconducts
A ‘magic angle’ lets electrons flow freely
By Emily Conover
4:10pm, March 8, 2018
graphene

DOUBLE UP  A device made of two layers of graphene (illustrated) can conduct electricity without resistance when one layer is rotated relative to the other.

Theasis/istockphoto

LOS ANGELES — Give a graphene layer cake a twist and it superconducts — electrons flow freely through it without resistance. Made up of two layers of graphene, a form of carbon arranged in single-atom-thick sheets, the structure’s weird behavior suggests it may provide a fruitful playground for testing how certain unusual types of superconductors work, physicist Pablo Jarillo-Herrero of MIT reported March 7 at a meeting of the American Physical Society.

The discovery, also detailed in two papers published online in Nature on March 5, could aid the search for a superconductor that functions at room temperature, instead of the chilly conditions required by all known superconductors. If found, such a substance could replace standard conductors in various electronics, promising massive energy savings.

Layered graphene’s superconductivity occurs when the second layer of graphene is twisted relative to the first, at a “magic angle” of about 1.1 degrees, and when cooled below 1.7 kelvins (about –271° Celsius). Surprisingly, Jarillo-Herrero and colleagues report, the same material can also be nudged into becoming an insulator — in which electrons are stuck in place — by using an electric field to remove electrons from the material. That close relationship with an insulator is a characteristic shared by certain types of high-temperature superconductors, which function at significantly warmer temperatures than other superconductors, although they still require cooling.

https://www.sciencenews.org/article/give-double-layer-graphene-twist-and-it-superconducts
....


APS March Meeting 2018
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session K35: 2D Materials - Superconductivity and Charge Density Waves I
8:00 AM–11:00 AM, Wednesday, March 7, 2018
LACC Room: 409B
Sponsoring Unit: DMP
Chair: Daniel Rhodes, Columbia Univ
Abstract: K35.00007 : Topology, correlations, and superconductivity in 2D
9:12 AM–9:48 AM
Abstract Presenter: Pablo Jarillo-Herrero (Physics, MIT)

In this talk I will review our recent quantum electronic transport experiments in a variety of 2D materials and van der Waals heterostructures, where we show interplay between topology, strong electron-electron correlations and electrically tunable superconductivity. In some of these materials, different phases can be achieved simply by tuning the electric field applied to the material.

http://meetings.aps.org/Meeting/MAR18/Session/K35.7

....

(more at link....)

Some high-temperature superconductors might not be so odd after all
Finding hidden swirls of electric current shows that the material’s behavior matches standard theory
By Emily Conover
7:00am, December 8, 2017
illustration of a superconductor

VORTEX FOUND Newly observed swirls of electric current in a high-temperature superconductor (shown in an artist’s conception) may indicate that the unusual material fits within the standard theoretical picture.

XAVIER RAVINET/UNIGE
Magazine issue: Vol. 193, No. 1, January 20, 2018, p. 11

A misfit gang of superconducting materials may be losing their outsider status.

Certain copper-based compounds superconduct, or transmit electricity without resistance, at unusually high temperatures. It was thought that the standard theory of superconductivity, known as Bardeen-Cooper-Schrieffer theory, couldn’t explain these oddballs. But new evidence suggests that the standard theory applies despite the materials’ quirks, researchers report in the Dec. 8 Physical Review Letters.

All known superconductors must be chilled to work. Most must be cooled to temperatures that hover above absolute zero (–273.15° Celsius). But some copper-based superconductors work at temperatures above the boiling point of liquid nitrogen (around –196° C). Finding a superconductor that functions at even higher temperatures — above room temperature — could provide massive energy savings and new technologies (SN: 12/26/15, p. 25). So scientists are intent upon understanding the physics behind known high-temperature superconductors.

When placed in a magnetic field, many superconductors display swirling vortices of electric current — a hallmark of the standard superconductivity theory. But for the copper-based superconductors, known as cuprates, scientists couldn’t find whirls that matched the theory’s predictions, suggesting that a different theory was needed to explain how the materials superconduct. “This was one of the remaining mysteries,” says physicist Christoph Renner of the University of Geneva. Now, Renner and colleagues have found vortices that agree with the theory in a high-temperature copper-based superconductor, studying a compound of yttrium, barium, copper and oxygen.

Vortices in superconductors can be probed with a scanning tunneling microscope. As the microscope tip moves over a vortex, the instrument records a change in the electrical current. Renner and colleagues realized that, in their copper compound, there were two contributions to the current that the probe was measuring, one from superconducting electrons and one from nonsuperconducting ones. The nonsuperconducting contribution was present across the entire surface of the material and masked the signature of the vortices.

Subtracting the nonsuperconducting portion revealed the vortices, which behaved in agreement with the standard superconductivity theory. “That, I think, is quite astonishing; it's quite a feat,” says Mikael Fogelström of Chalmers University of Technology in Gothenburg, Sweden, who was not involved with the research.

https://www.sciencenews.org/article/some-high-temperature-superconductors-might-not-be-so-odd-after-all

It is curious that the bigger "lattice" type molecules often display "superconducting" properties at very cold temps. I wonder if at cold temps/high pressure they just become charge-field tamped down "blocks" and certain charge field streams then just penetrate across these non-cycling or reduced cycling atom-blocks (charge field reduced cold atoms). Basically, "recycling" per Mathis stops and then flow occurs around the "semi-frozen" atoms? In many of these cases, the charge cycling balance is off.


(Miles)
Europium
Atomic Number: 63

240c. Period 6 Why Isn't Hafnium a Noble Gas?
http://milesmathis.com/haf.pdf
We have more evidence of my diagrams from Europium, whose density goes way down compared to Samarium. That is because Samarium has gone all blue in the inner levels, with two protons on both sides of each inner hole. That only gives us four parcels of charge through a hole that can take five, but remember, this 5-stack contains a single proton, and that proton is not part of an alpha. This means that there is charge leakage around that inner proton (in the sandwich), so the 5-stack can't really channel 5 proton's worth of charge. The inner proton channels, but it doesn't spin up the charge a fifth amount. So the charge strength of the 5-stack stays at 4. Therefore, Europium is actually at its inner limit. It can't put any more protons in the inner levels. So it switches to a different plan, one more like we saw with Dysprosium:

We can see why that is considerably less dense, since it has more mass out in the 4th level and less on the axis. We can also see that Europium now has enough protons to work with that it can bump up all the numbers in the 4th level by one. In this way, it avoids having the same number at each pole. Instead of 1 North and two South, it has 2 north and 3 South. That solves the problem of equal charge.

This means that once again Europium isn't doing what it is doing to find a +3 oxidation number. That is just a side-effect of a deeper mechanics.

....
Notes on Dysprosium as SC:


Journal of Inorganic and Organometallic Polymers and Materials

September 2012, Volume 22, Issue 5, pp 1081–1086 | Cite as
Growth of the Dysprosium–Barium–Copper Oxide Superconductor Nanoclusters in Biopolymer Gels

Clusters of DyBa2Cu3O7−y high TC type II nanosuperconductor were prepared by sol–gel method in the presence of biopolymer chitosan. At the first step, the precursor and biopolymer were aggregated into amorphous matrix and then hydrogels were formed by thermogelling. Nucleation and growth of discrete nanoparticles is controlled by the biopolymer gel owing to retention of the fibrous nature of the chitosan at high temperatures up to 500 °C. After heating to 900 °C and complete decomposition of BaCO3, nanoparticles of DyBa2Cu3O7−y superconductor with diameter of 10–20 nm in the form of nanoclusters are prepared. Critical temperature (Tc) of the nanoparticles was found to be above 83 K. Characterizations of specimens were performed using scanning electron microscopy and transmission electron microscopy, supported by other techniques including XRD diffraction, energy dispersive X-ray, FT-IR spectrum and magnetic susceptibility measurements.

https://rd.springer.com/article/10.1007%2Fs10904-012-9687-7

July 2016, Volume 29, Issue 7, pp 1787–1791 | Cite as
The Effect of Dy Doping on the Magnetic Behavior of YBCO Superconductors

Abstract

The effect of dysprosium (Dy) doping on yttrium barium copper oxide (YBCO) prepared by conventional solid-state reaction method has been investigated by means of XRD, AC susceptibility, and DC magnetization measurements. AC susceptibility measurements for sintered YBCO pellets have been performed as a function of temperatures at constant frequency and AC field amplitude in the absence of a DC bias field. DC magnetization measurements were done at 5, 20, and 77 K upon zero field cooling (ZFC) process. The magnetization measurements showed a paramagnetic behavior existing at high magnetic fields. The magnetic field dependence of critical current density of the samples has been estimated from DC magnetization data. The partial Dy substitution for Y on YBCO superconductors improves the bulk critical current density at high magnetic fields and at high-temperature regions (higher than 20 K).

https://link.springer.com/article/10.1007/s10948-016-3493-3

....
Posted: May 16, 2009
Europium found to be a superconductor
(Nanowerk News) Of the 92 naturally occurring elements, add another to the list of those that are superconductors.

James S. Schilling, Ph.D., professor of physics in Arts & Sciences at Washington University in St. Louis, and Mathew Debessai, Ph.D., — his doctoral student at the time — discovered that europium becomes superconducting at 1.8 K (-456 °F) and 80 GPa (790,000 atmospheres) of pressure, making it the 53rd known elemental superconductor and the 23rd at high pressure.

Debessai, who received his doctorate in physics at Washington University's Commencement May 15, 2009, is now a postdoctoral research associate at Washington State University.

"It has been seven years since someone discovered a new elemental superconductor," Schilling said. "It gets harder and harder because there are fewer elements left in the periodic table."

This discovery adds data to help improve scientists' theoretical understanding of superconductivity, which could lead to the design of room-temperature superconductors that could be used for efficient energy transport and storage.

The results are published in the May 15, 2009, issue of Physical Review Letters in an article titled "Pressure-induced Superconducting State of Europium Metal at Low Temperatures."

Schilling's research is supported by a four-year $500,000 grant from the National Science Foundation,Division of Materials Research.

Europium belongs to a group of elements called the rare earth elements. These elements are magnetic; therefore, they are not superconductors.

"Superconductivity and magnetism hate each other. To get superconductivity, you have to kill the magnetism," Schilling explained.

Of the rare earths, europium is most likely to lose its magnetism under high pressures due to its electronic structure. In an elemental solid almost all rare earths are trivalent, which means that each atom releases three electrons to conduct electricity.

"However, when europium atoms condense to form a solid, only two electrons per atom are released and europium remains magnetic. Applying sufficient pressure squeezes a third electron out and europium metal becomes trivalent. Trivalent europium is nonmagnetic, thus opening the possibility for it to become superconducting under the right conditions," Schilling said.

Schilling uses a diamond anvil cell to generate such high pressures on a sample. A circular metal gasket separates two opposing 0.17-carat diamond anvils with faces (culets) 0.18 mm in diameter. The sample is placed in a small hole in the gasket, flanked by the faces of the diamond anvils.
Pressure is applied to the sample space by inflating a doughnut-like bellow with helium gas. Much like a woman in stilettos exerts more pressure on the ground than an elephant does because the woman's force is spread over a smaller area, a small amount of helium gas pressure (60 atmospheres) creates a large force (1.5 tons) on the tiny sample space, thus generating extremely high pressures on the sample.

Unique electrical, magnetic properties

Superconducting materials have unique electrical and magnetic properties. They have no electrical resistance, so current will flow through them forever, and they are diamagnetic, meaning that a magnet held above them will levitate.

These properties can be exploited to create powerful magnets for medical imaging, make power lines that transport electricity efficiently or make efficient power generators.

However, there are no known materials that are superconductors at room temperature and pressure. All known superconducting materials have to be cooled to extreme temperatures and/or compressed at high pressure.

"At ambient pressure, the highest temperature at which a material becomes superconducting is 134 K (-218 °F). This material is complex because it is a mixture of five different elements. We do not understand why it is such a good superconductor," Schilling said.

Scientists do not have enough theoretical understanding to be able to design a combination of elements that will be superconductors at room temperature and pressure. Schilling's result provides more data to help refine current theoretical models of superconductivity.

"Theoretically, the elemental solids are relatively easy to understand because they only contain one kind of atom," Schilling said. "By applying pressure, however, we can bring the elemental solids into new regimes, where theory has difficulty understanding things.

"When we understand the element's behavior in these new regimes, we might be able to duplicate it by combining the elements into different compounds that superconduct at higher temperatures."
Schilling will present his findings at the 22nd biennial International Conference on High Pressure Science and Technology in July 2009 in Tokyo, Japan.

https://www.nanowerk.com/news/newsid=10666.php

28 August 1993
Technology: US Navy superconductor sails past Britain

By ELISABETH GEAKE

The US Navy is pioneering the use of high-temperature superconductors
in working machinery with a newly delivered sonar system. Now British scientists
are urging the government to fund more research into superconductivity.

Meanwhile the American Superconductor Corporation of Westboro, Massachusetts,
and the US Naval Undersea Warfare Center, based in Connecticut, have finished
a prototype sonar system incorporating bismuth strontium copper oxide, which
is superconducting at 73 K (-200 °C). It was delivered two years ahead
of schedule.

Nick Kerley of Oxford Instruments in Eynsham says, ‘It is a very good
demonstrator for high-temperature superconductors. The message (is) that
real practical devices are beginning to appear on the horizon – it is no
longer a dream.’ He was among the group who visited the US, and says Britain
must now decide on a device which is within its capabilities, and start
making a prototype by the end of the year. ‘I’d like to think the DTI would
be influenced and call for demonstration proposals,’ he says. Tim Button
of ICI Superconductors in Billingham, Cleveland, thinks the DTI may act
more quickly now, but he says: ‘I always felt it was urgent anyway. The
science isn’t any better in the US but the transfer into usable technology
is strides ahead of what we could do.’

The American instrument is an acoustic transducer, which converts electrical
energy into sound waves. It is used in sensitive sonar systems probing shallow
seas, such as the Persian Gulf. The company says this is the first time
high-temperature superconductors, which lose all their electrical resistance
at temperatures below about 113 K, have been combined with the ordinary
room-temperature electronics that control them. The transducer, which cost
$800 000, is similar to a hi-fi speaker: it has a coil made of the superconductor
and generates a magnetic field when an alternating electric current passes
through it. Inside the coil is a rod of terbium dysprosium, which is a magneto-strictive
material – its length changes with the magnetic field. The rod is connected
to pistons immersed in the sea, whose movements generate sound waves. The
US Navy has tested it successfully in a 30-metre-deep test lake.

The superconductor is refrigerated at between 50 and 70 K, which is
also the optimum operating temperature for the terbium rod. ‘The marriage
of the high-temperature superconductor and the terbium dysprosium gives
rise to low frequencies and high powers not available before,’ says Greg
Yurek, the company president. This means the system can detect quiet submarines.
A coil made from an ordinary conductor such as copper would overheat from
the electric current, while one made of a low-temperature superconductor,
which is only superconducting up to about 10 K, would be too expensive to
cool.

https://www.newscientist.com/article/mg13918883-000-technology-us-navy-superconductor-sails-past-britain/

Terbium–neodymium co-doping in Bi sites on the BPSCCO bismuth cuprate superconductor

Morsy M A Sekkina, Hosny A El-Daly and Khaled M Elsabawy1

Published 19 November 2003 • 2004 IOP Publishing Ltd
Superconductor Science and Technology, Volume 17, Number 1

Abstract

The parent BiPbSr2Ca2Cu3O10 (BPSCCO) and samples of the general formula Bi1-(x+y)NdxTbyPbSr2Ca2Cu3O10, where x = y = 0.05, 0.1 and 0.2, were prepared using the conventional high-temperature solid-state reaction technique. The superconducting measurements proved that the best value of Tc, 108 K, is for the sample with x = y = 0.1 mol% while the lowest value of Tc, 101 K, is for the sample with maximum dopant concentration x = y = 0.2 mol%. The evaluated crystalline lattice structure of the prepared samples mainly belongs to the superconductive tetragonal phase (2223) besides the secondary (2212) phase. Also, thermogravimetric and differential thermal analyses were studied on the green mixture showing an endothermic peak at 790 °C corresponding to the superconductive phase formation. The microstructures of the prepared samples were investigated by scanning electron microscopy and energy dispersive x-ray analysis.

http://iopscience.iop.org/article/10.1088/0953-2048/17/1/016

The Ytterby Elements

About a half hours drive out of Stockholm, Sweden, there’s a tiny nondescript town. During the 18th – 20th centuries there was slightly more life here, with a mine operating out of the town.


Ytterby mine, roughly 1910. Courtesy of Tekniska museet on Flickr

One day in 1787, Carl Arrhenius, an army lieutenant, discovered a strange, unusually heavy black ore in the mine. Over the next 100 years, many different elements where discovered from this one ore, later named gadolinite.

These elements are all “rare earth” elements, which, despite the name, are not particularly rare. Their rarity comes more from the difficulty in separating them from each other. It took many scientists many years of research and arguing to discover them all.

Now the little town of Ytterby is not the first place you’d pick to hold a scientific record. Yet it does, as it’s the origin of the names of not one, but four elements. Of the elements in the original gadolinite ore, yttrium, terbium, erbium, and ytterbium all ended up named after the town.

Yttrium

The first element in Ytterby’s story is yttrium. A Finnish chemist, Johan Gadolin, received a sample of the mysterious black ore from Arrhenius. He isolated an unknown element – which later become known as yttrium.

Yttrium’s claim to fame is a discovery made two centuries later in 1987. Yttrium barium copper oxide, a material containing yttrium, is a superconductor at “high” temperatures. Superconductors are strong magnets at low temperatures, and are used in places like in MRIs in hospitals. It is worth noting that to scientists researching superconductors, -180ºC is a high temperature, although to anyone else on the planet it seems freezing. This is because to reach these temperatures, it needs liquid helium cooling. As liquid helium is both expensive and in short supply, hopefully a material like this will soon replace conventional superconductors in MRIs and scientific instruments.

A superconductor becomes magnetic at low temperatures and floats above another magnet. Courtesy of Trevor Prentice on Flickr

Terbium

Further along the table lives terbium. Another Swedish man called Carl, this time Carl Gustaf Mosander, found two more elements in the black gadolinite. A thoroughly unimaginative guy, he named all three after the mine where they were first found – naming Gadolin’s element yttrium, and the other two terbium and erbium.

Terbium is another rare-earth, and is often used in TV screens to make yellow and green phosphors. It’s also mixed with blue and red phosphors to make white light in LEDs.
SONY DSC

Terbium sulfate glowing green under UV light. Terbium green is often used in TV phosphors. Credit Chemical Elements, A Virtual Museum

Terbium is versatile, and can also be used in single molecules that act as tiny bar magnets. Usually magnets need hundreds and thousands of individual atoms or molecules. One of these terbium molecules can instead act as a magnet on its own.

The reason why this is important is due to the device you’re reading this on. The storage in computers and phones is made up of tiny little magnetic areas coded with data. These magnetic bits have gotten smaller and smaller as well as faster with time, as computers have gone from filling an entire room to fitting in your pocket. We are now reaching the limit of how small we can make these magnets, but imagine if single molecules could be used instead! With terbium, the dream of minuscule computers may come true.

Erbium

Now erbium is just confusing! The name, as you may have noticed, is very close to that of terbium. This led to some mishaps when the two where first discovered.

Out of the black gadolinite came different coloured element oxides. The original “erbium” was the yellowish coloured stuff, while “terbium” the bright pink stuff. These two were simple enough to separate from the white yttrium. However, when they were discovered people weren’t convinced that they were two separate elements, and by the time they sorted it out, the original names were switched!

These days, erbium refers to the element whose salts are a beautiful rose-pink. If you buy a pair of rose-coloured glasses, chances are there’s erbium!

Small amounts of erbium are also used with yttrium in Er:YAG lasers. They’re useful because the light from these lasers doesn’t travel through the human body. They are therefore useful for dermatology and dentistry, where only the skin or surface of a tooth needs to be treated.

A rare earth (neodymium and yttrium Nd:YAG) laser. Similar lasers are made with erbium or ytterbium and yttrium. Courtesy of Ben Williams on Flickr

Ytterbium

Finally, we have ytterbium. Ytterbium was discovered a lot later than the other three elements, from a sample of erbium by a Swiss chemist Jean Charles Galissard de Marignac. Just like Mosander, he had little imagination, and decided again to name the element after the town.

Ytterbium is also used like erbium in yttrium-based Yb:YAG lasers. Its most interesting use though is in atomic clocks.

Atomic clocks use a vibrating atom to keep time. The ytterbium clock is even more accurate than the caesium atomic clock currently used to define the second. This improved accuracy means that super super fast things in earth sciences and astronomy can be measured.

The Ytterby elements in the lab. Author’s own

Countless other applications of these Ytterby elements exist, and they’re the focus of a lot of research. Any dedicated rare-earth chemist will eventually make the trip to Ytterby to visit the birthplace of these versatile elements.

However, the story doesn’t end with these four. From gadolinite and the mine in Ytterby, 6 other rare-earth elements were discovered:

Scandium: named after Scandinavia

Gadolinium: named after Johan Gadolin

Dysprosium: from the Greek “hard to find”

Holmium: named after Stockholm county, where Ytterby is found

Thulium: after “Thulia”, a Greek name for Scandinavia

Lutetium: from the Latin name for Paris (where the mineral sample was analysed)

https://blogs.unimelb.edu.au/sciencecommunication/2016/10/15/the-ytterby-elements/

Polonium's Superconductivity
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Quasi-two-dimensional superconductivity from dimerization of atomically ordered AuTe2Se4/3 cubes
J. G. Guo ORCID: orcid.org/0000-0003-3880-30121, X. Chen ORCID: orcid.org/0000-0003-3477-22041,2, X. Y. Jia3, Q. H. Zhang1, N. Liu1,2, H. C. Lei4, S. Y. Li3,5, L. Gu1,6,7, S. F. Jin1,6 & X. L. Chen1,6,7

Nature Communicationsvolume 8, Article number: 871 (2017)
doi:10.1038/s41467-017-00947-0
Download Citation

Abstract

The emergent phenomena such as superconductivity and topological phase transitions can be observed in strict two-dimensional (2D) crystalline matters. Artificial interfaces and one atomic thickness layers are typical 2D materials of this kind. Although having 2D characters, most bulky layered compounds, however, do not possess these striking properties. Here, we report quasi-2D superconductivity in bulky AuTe2Se4/3, where the reduction in dimensionality is achieved through inducing the elongated covalent Te–Te bonds. The atomic-resolution images reveal that the Au, Te, and Se are atomically ordered in a cube, among which are Te–Te bonds of 3.18 and 3.28 Å. The superconductivity at 2.85 K is discovered, which is unraveled to be the quasi-2D nature owing to the Berezinsky–Kosterlitz–Thouless topological transition. The nesting of nearly parallel Fermi sheets could give rise to strong electron–phonon coupling. It is proposed that further depleting the thickness could result in more topologically-related phenomena.

Introduction

The dimensional reduction or degeneracy usually induces the significant change of electronic structure and unexpected properties. The monolayer, interface and a few layers of bulky compounds are typical resultant forms of low dimensionality. The two dimensional (2D) material, for instance, graphene, is found to have a linear energy dispersion near Fermi energy (EF) and possess a number of novel properties1,2,3. Monolayer MoS2 exhibits a direct energy gap of 1.8 eV4 and pronounced photoluminescence5, in contrast to trivial photo-response in bulky MoS2 with an indirect band-gap.

2D superconductivity (SC), a property closely related to dimensional reduction, has been observed in a variety of crystalline materials like ZrNCl6, NbSe27, and MoS28 recently through the electric-double layer transistor (EDLT)9 technique. Many emerged properties, i.e., the well-defined superconducting dome, metallic ground state and high upper critical field6, 8, significantly differ from those of intercalated counterparts. Besides, the lack of in-plane inversion symmetry in the outmost layer of MoS2/NbSe2 with strong Ising spin-orbital coupling induces a valley polarization7, 8. In the scenario of low-dimensional interface, the unexpected 2D SC10, 11, the remarkable domed-shaped superconducting critical temperature (Tc)12, pseudo-gap state13, and quantum criticality14 have been demonstrated in La(Al,Ti)O3/SrTiO3(001) film. Very recently, the interface between Bi2Te3 and FeTe thin films displayed 2D SC evidenced by Berezinsky–Kosterlitz–Thouless (BKT) transition at 10.1 K15. The tentative explanations are related to the strong Rashba-type spin–orbit interactions in the 2D limit.

At the moment, the way to fabricating low-dimensional materials generally involves molecule beam epitaxy and exfoliation from the layered compounds. The top-down reduction processes usually are sophisticated and time consuming for realizing scalable and controllable crystalline samples. There are other chemical routes to tuning dimensionality by means of either changing the size of intercalated cations or incorporating additional anions. It is reported that increasing the size of alkaline-earth metals Ae (Ae=Mg, Ca, and Ba) between [NiGe] ribbons can reduce three dimensional (3D) structure to quasi-1 dimensional one16. In addition, the ternary CaNiGe can be converted into ZrCuSiAs-type CaNiGeH by forming additional Ca–H bonds, which exhibits different properties owing to the emergence of 2D electronic states17. The metastable Au1−x Te x (0.6 < x < 0.85) show an α-type polonium structure18, 19, in which the Au and Te disorderly locate at the eight corners of a simple cubic unit cell. The Tc fluctuates in the range of 1.5–3.0 K, but the mechanism of SC has been barely understood20. Besides, the equilibrium phase AuTe2, known as calaverite, is a non-superconducting compound, in which distorted AuTe6 octahedra are connected by Te–Te dimers21.

Through incorporating more electronegative Se anions, we fabricate a new layered compound AuTe2Se4/3 by conventional high temperature solid-state reaction. In a basic cube subunit, the Se anions attract electrons from Te and lead to the ordered arrangement of Au, Te and Se atoms. The cubes stack into strip through Te–Te dimers at 3.18 Å and 3.28 Å along the a- and b-axis, respectively, which composes 2D layers due to the existence of weak Te–Te interaction (~4 Å) along the c-axis. Electrical and magnetic measurements demonstrate that the SC occurs at 2.85 K. Furthermore, this SC exhibits 2D nature evidenced by the BKT transition in the thin crystals. The observed results are interpreted according to the crystallographic and electronic structure in reduced-dimensionality.

https://www.nature.com/articles/s41467-017-00947-0

Hydrogen‐rich superconductors at high pressures
Advanced Review
Hui Wang, Xue Li, Guoying Gao, Yinwei Li, Yanming Ma
Published Online: Sep 05 2017
DOI: 10.1002/wcms.1330

Abstract

The hydrogen‐rich superconductors stabilized at high‐pressure conditions have been the subject of topic interests. There is an essential hope that hydrogen‐rich superconductors are promising candidates of room‐temperature superconductors. Recent advances in first‐principles crystal structure prediction techniques have opened up the possibility of reliable prediction of superconductive structures, and subsequent superconductivity calculations based on phonon‐mediated superconducting mechanism revealed a general appearance of high temperature superconductivity in pressurized hydrides. Theory‐orientated experiments at high pressure discovered a number of hydrogen‐rich superconductors, among which sulfur hydrides exhibit a remarkably high superconducting critical temperature reaching 203 K. In this review, we discuss the emerging research activities towards hydrogen‐rich superconductors at high pressures and outlook the future direction in the field. WIREs Comput Mol Sci 2018, 8:e1330. doi: 10.1002/wcms.1330

This article is categorized under:

   Structure and Mechanism > Computational Materials Science

Images
The crystal structure of (a) the Pm‐3n phase of YH3, (b) the Im‐3m phase of H3S, (c) the R‐3m phase of H3S, (d) the P63/mmm phase of TeH4, (e) the Cmmm phase of RbH3, (f) the Cc phase of H5Cl, (g) the Im‐3m phase of CaH6, and (h) the I4/mmm phase of CaH4. Hydrogen and the heavier element are shown by the small and large balls, respectively.
[ Normal View | Magnified View ]
(a) Calculated PHDOS (top panel) and the Eliashberg phonon spectral function α2F(ω)/ω, electron–phonon integral λ(ω) (lower panel) of SiH4(H2)2 at 250 GPa. (b) Top panel is the collected estimated Tc values of SiH4(H2)2, GeH4(H2)2, and AlH3H2 at 250 GPa, and the lower panel describes the contributions of the low‐frequency vibrations from heavy atoms (green bars), the intermediate‐frequency intermolecular vibrations (blue bars), and the high‐frequency phonons from the H2 vibrons (yellow bars) to the total λ.
[ Normal View | Magnified View ]
(a) Calculated PHDOS (top panel) and the Eliashberg phonon spectral function α2F(ω)/ω, electron–phonon integral λ(ω) (lower panel) of AsH8 at 350 GPa. (b) Top panel is the collected estimated Tc values of H4I, PoH4, LiH6, PbH8, AsH8, and MgH12 at selected pressures, and the lower panel describes the contributions of the low‐frequency vibrations from metal atoms (green bars), the intermediate‐frequency intermolecular vibrations (blue bars), and the high‐frequency phonons from the H2 vibrons (yellow bars) to the total λ.
[ Normal View | Magnified View ]
(a) The crystal structure and electron localization function of the Im‐3m phase of CaH6. (b) Phonon dispersion curves of Im‐3m‐CaH6 (left panel). Olive circles indicate the phonon line width with a radius proportional to the strength. Calculated Eliashberg phonon spectral function α2F(ω) and electron–phonon integral λ(ω) (right panel). Band structures of (c) CaH6 and (d) Ca0H6 (Im‐3m‐CaH6 with Ca removed), respectively.
[ Normal View | Magnified View ]
(a) The crystal structure and electron localization function (ELF) of the Im‐3m phase of H3S. (b) Calculated Eliashberg phonon spectral function α2F(ω) and electron–phonon integral λ(ω) (top panel) and the PHDOS (lower panel) of Im‐3m‐H3S at 200 GPa. (c) The crystal structure of the Pm‐3n phase of GaH3. (d) Calculated Eliashberg phonon spectral function α2F(ω)/ω and electron–phonon integral λ(ω) (top panel) and the PHDOS (lower panel) of Pm‐3n‐GaH3 at 160 GPa.
[ Normal View | Magnified View ]

References

http://wires.wiley.com/WileyCDA/WiresArticle/wisId-WCMS1330.html
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Ionic hydrides

Ionic or saline hydrides are composed of hydride bound to an electropositive metal, generally an alkali metal or alkaline earth metal. The divalent lanthanides such as europium and ytterbium form compounds similar to those of heavier alkali metal. In these materials the hydride is viewed as a pseudohalide. Saline hydrides are insoluble in conventional solvents, reflecting their non-molecular structures. Ionic hydrides are used as bases and, occasionally, as reducing reagents in organic synthesis.[6]

C6H5C(O)CH3 + KH → C6H5C(O)CH2K + H2

Typical solvents for such reactions are ethers. Water and other protic solvents cannot serve as a medium for ionic hydrides because the hydride ion is a stronger base than hydroxide and most hydroxyl anions. Hydrogen gas is liberated in a typical acid-base reaction.

NaH + H2O → H2 (g) + NaOH ΔH = −83.6 kJ/mol, ΔG = −109.0 kJ/mol

Often alkali metal hydrides react with metal halides. Lithium aluminium hydride (often abbreviated as LAH) arises from reactions of lithium hydride with aluminium chloride.

4 LiH + AlCl3 → LiAlH4 + 3 LiCl
............

Pseudohalogen
From Wikipedia, the free encyclopedia

The pseudohalogens are polyatomic analogues of halogens, whose chemistry, resembling that of the true halogens, allows them to substitute for halogens in several classes of chemical compounds[1]. Pseudohalogens occur in pseudohalogen molecules, inorganic molecules of the general forms Ps–Ps or Ps–X (where Ps is a pseudohalogen group), such as cyanogen; pseudohalide anions, such as cyanide ion; inorganic acids, such as hydrogen cyanide; as ligands in coordination complexes, such as ferricyanide; and as functional groups in organic molecules, such as the nitrile group. Well-known pseudohalogen functional groups include cyanide, cyanate, thiocyanate, and azide.
https://en.wikipedia.org/wiki/Pseudohalide

WHAT'S HOT IN... PHYSICS , May/Jun 2009
The Good Samarium Hots Up Superconductivity
by Simon Mitton

The Physics Hot Papers in this period show that superconductivity research is now hotting up, thanks to the unexpected discovery of a new class of iron-based superconductors. Papers #2, #3, #7 and #9 capture the tremendous interest stimulated by the recent discovery of superconductivity at Tc = 26 K in Hideo Hosonothe iron-based oxypnictide La(O1-xFx)FeAs (Y. Kamihari, et al., J. Am. Chem. Soc., 130 [11]: 3296-7, 2008; currently #1 in the Chemistry Top Ten). That research, by Hideo Hosono and colleagues of the Tokyo Institute of Technology, put high-temperature superconductivity back on the agenda with a bang.

Paper #2 describes an experiment designed by Xian Hui Chen, and conducted together with colleagues at the University of Science and Technology, Hefei, China. They followed up on the Japanese discovery paper by looking at superconductivity in a related compound, SmFeAsO1-x Fx, in which samarium is substituted for lanthanum. They aimed to see how high they could push Tc in Jonathan Baggera layered rare-earth superconductor. In doing so they broke the record for a non-copper-oxide superconductor, by reaching Tc = 43 K, comfortably above the previous record of 39 K for magnesium diboride.

The Sm-doped material is intriguing: according to Chen, it has Tc above that suggested by standard BCS theory, which argues for the oxypnictides being unconventional superconductors. Furthermore, the jump in Tc from 26 K to 43 K just by substituting Sm for La immediately suggested that further research would produce higher Tc in layered oxypnictides doped with F.

That’s where #3 takes us: in it Zhi-An Ren and colleagues from Beijing, China, report Tc = 55 K in the same F-doped compound. In fact, related experiments by this group, in which they also substituted Ce, Pr, and Nd, have shown that FeAs superconductors constitute a new family with Tc > 50 K. The high-citation rate of #3 is partly driven by the comprehensive information it gives on fabrication. The materials are grown using a high-pressure technique similar to that used for turning graphite to diamond.

Zhi-An Ren’s collaboration is also responsible for #7, in which they point out that the compounds have a simple structure of alternating FeAs and ReO layers (where Re is a rare earth). Instead of doping with F to achieve superconductivity, they created vacancies of oxygen atoms in the lattice. That move creates more electron carriers, which should be a more efficient approach to the realization of superconductivity. And indeed, tuning the O content leads to the occurrence of superconductivity in a way that resembles the situation in cuprates. That’s encouraging because the parallels between the two compounds suggest that the arsenides with O vacancies rather than F doping could be the more competitive choice for higher Tc.

Newcomer #9 is a paper that neatly illustrates how research on F-doped arsenides may contribute to fundamental physics. The experiments described in this paper show how F doping suppresses spin-density-wave (SDW) instabilities and leads to superconductivity. SDW is a low-energy ordered state that occurs at low temperatures. SDW inhibits the onset of superconductivity.

Superconductivity is one of the most dramatic phenomena in condensed matter physics. Part of the motivation for the groups in China and Japan is the ultimate goal: the realization of the phenomenon at room temperature. There are plenty of physicists who will state informally that room temperature operation is about as likely as cold fusion, or hot fusion. But fast progress has energized research. In 2008 there were at least seven international symposia devoted to Fe-based superconductors, and those events have no doubt propelled the citation rates. For researchers it’s a matter of striking while the iron is hot!

Dr. Simon Mitton is a Fellow of St. Edmund’s College, Cambridge, U.K.

http://archive.sciencewatch.com/ana/hot/phy/09mayjun-phy/

Princeton’s Robert Cava: From Superconductivity to Topological Insulators
Scientist Interview: March 2011

SW: What do you consider the critical questions in high-Tc that still have to be answered?

Well, why do these things superconduct at all, and what’s going on in these materials at a very, very local scale? The most interesting physics is probably occurring at a scale of tens of angstroms. You can see wonderfully complicated things going on at the nanometer-length scale with different kinds of experimental probes. It’s not just a uniform sea of electrons like we learned a piece of copper is. It’s a very inhomogeneous distribution of electrons doing all kinds of crazy stuff. The more people look, the more complicated it gets.

SW: Are any researchers seriously looking for new high-Tc superconductors anymore, or is that part also done?

A small number of people are, and every once in a while a big surprise appears—somebody finds a new superconductor that nobody expected. In 2008, for example, a Japanese group found a new superconductor, a combination of iron, arsenic, lanthanum, oxygen, and fluorine that was superconducting at 26 Kelvin. What made it so interesting is that the superconductor seems to arise from the iron and arsenic, and the iron should typically give you a magnet.

Until the high-temperature superconductors came along, people thought magnetism and superconductivity were incompatible, whereas in many cases they’re probably just two sides of the same coin. You can change a magnet into a superconductor and a superconductor into a magnet by changing some chemical parameter.

So in 2008, a group of Japanese researchers discovered that iron and arsenic are the basis of a new class of superconductors whose superconductivity and magnetism seem to be related (Y. Kamihara, et al., J. Am. Chem. Soc., 130[11]: 3296-7, 2008; see also ).

After that big discovery, another group discovered that the temperature of the superconductor could go up to 50 or 60 Kelvin with the right combination of elements. That makes these the second-highest-temperature superconductors known, and with a whole new element involved—not copper anymore, but iron.

Of course, thousands of people also jumped onto this new one really fast. The interesting difference between now and 1986 is that back then you had to hear about the discovery through word of mouth. Somebody talked to somebody who talked to somebody on the other side of the world. Occasionally, a fax of a preprint appeared. Information didn’t travel very fast.

SW: Let’s begin at the beginning. How far have high-temperature superconductors come in the quarter-century since they were discovered, and what are the key research areas still being studied?

I’d say there are a couple of things that are still going on. First, there’s no universally accepted theory yet about why they work. We know a lot about them, and we have much of the phenomenology worked out, but we still have no theory about what makes them superconducting that the community as a whole accepts. That’s a remarkable situation, if you ask me. It goes to show how complicated physics can be sometimes.

There are so many interesting phenomena that occur in conjunction with the superconductivity that the whole package has not really been put together yet in a way that satisfies everybody, at least not like the BCS theory explains basic superconductivity. There’s nothing yet established that will go into the textbooks as explaining it. There’s a lot of action on the theoretical side, and it’s very sophisticated, but nobody has explained it all.

http://archive.sciencewatch.com/inter/aut/2011/11-mar/11marCava/

The Arsenic-Iron SC connection with unified alphas...cycling contained at pressure?

https://www.nevyns-lab.com/mathis/app/AtomicViewer/AtomicViewer.php?metadata=false&element=33&position=0,0,60
https://www.nevyns-lab.com/mathis/app/AtomicViewer/AtomicViewer.php?metadata=false&element=26&position=0,0,60

Physicists find clues to the origins of high-temperature superconductivity
January 18, 2018 by Lisa Zyga, Phys.org feature
cuprate superconductors

Figure showing the conversion between incoherent and coherent electron correlations in the cuprates’ non-superconducting and superconducting states, respectively. Credit: Li et al. Published in Nature Communications.

Ever since cuprate (copper-containing) superconductors were first discovered in 1986, they have greatly puzzled researchers. Cuprate superconductors have critical superconducting temperatures—the point at which their electrical resistance drops to zero—of up to 138 K at ambient pressure, which far exceeds the critical temperatures of other superconductors and is even higher than what is thought possible based on theory.

Now in a new study, researchers have discovered the existence of a positive feedback loop that greatly enhances the superconductivity of cuprates and may shed light on the origins of high-temperature cuprate superconductivity—considered one of the most important open questions in physics.

The researchers, Haoxiang Li et al., at the University of Colorado at Boulder and the École Polytechnique Fédérale de Lausanne, have published a paper on their experimental ARPES (Angle Resolved Photoemission Spectroscopy) results on high-temperature cuprate superconductors in a recent issue of Nature Communications.

As the researchers explain, the positive feedback mechanism arises from the fact that the electrons in the non-superconducting cuprate state are correlated differently than in most other systems, including in conventional superconductors, which have strongly coherent electron correlations. In contrast, cuprates in their non-superconducting state have strongly incoherent "strange-metal" correlations, which are at least partly removed or weakened when the cuprates become superconducting.

Due to these incoherent electron correlations, it has been widely believed that the framework that describes conventional superconductivity—which is based on the notion of quasiparticles—cannot accurately describe cuprate superconductivity. In fact, some research has suggested that cuprate superconductors have such unusual electronic properties that even attempting to describe them with the notion of particles of any kind becomes useless.

This leads to the question of, what role, if any, do the strange-metal correlations play in high-temperature cuprate superconductivity?

The main result of the new paper is that these correlations don't simply disappear in the cuprate superconducting state, but instead get converted into coherent correlations that lead to an enhancement of the superconductive electron pairing. This process results in a positive feedback loop, in which the conversion of the incoherent strange-metal correlations into a coherent state increases the number of superconductive electron pairs, which in turn leads to more conversion, and so on.

The researchers found that, due to this positive feedback mechanism, the strength of the coherent electron correlations in the superconducting state is unprecedented, greatly exceeding what is possible for conventional superconductors. Such a strong electron interaction also opens up the possibility that cuprate superconductivity might occur due to a completely unconventional pairing mechanism—a purely electronic pairing mechanism that could arise solely due to quantum fluctuations.

"We experimentally discover that the incoherent electron correlations in the strange metal 'normal state' are converted to coherent correlations in the superconducting state that help strengthen the superconductivity, with an ensuing positive feedback loop," coauthor Dan Dessau at the University of Colorado at Boulder told Phys.org. "Such a strong positive feedback loop should strengthen most conventional pairing mechanisms but could also allow for a truly unconventional (purely electronic) pairing mechanism."

(more at link...)

https://phys.org/news/2018-01-physicists-clues-high-temperature-superconductivity.html

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Scientists find new magnetic state in iron-based superconductor
27 February 2018

The Ames scientists created a variant of the iron arsenide CaKFe4As4 by substituting in cobalt and nickel at precise locations. This slightly distorted the atomic arrangements, inducing the new magnetic order while retaining the material’s superconducting properties. Image: Ames Laboratory, US Department of Energy.

Scientists at the US Department of Energy's Ames Laboratory have discovered a state of magnetism that may be the missing link in understanding the relationship between magnetism and unconventional superconductivity. The research, recently reported in a paper in Nature Quantum Materials, provides tantalizing new possibilities for attaining superconducting states in iron-based materials.

"In the research of quantum materials, it's long been theorized that there are three types of magnetism associated with superconductivity," explained Paul Canfield, a senior scientist at Ames Laboratory and a distinguished professor of physics and astronomy at Iowa State University. "One type is very commonly found, another type is very limited and only found in rare situations, and this third type was unknown, until our discovery."

The scientists suspected that the material they studied, the iron arsenide CaKFe4As4, was such a strong superconductor because there was an associated magnetic ordering hiding nearby. Creating a variant of the material by substituting in cobalt and nickel at precise locations, known as ‘doping’, slightly distorted the atomic arrangements, which induced the new magnetic order while retaining the material’s superconducting properties.

(more at link...)
https://www.materialstoday.com/metals-alloys/news/new-magnetic-state-ironbased-superconductor/

Physicists "learn the rules" of magnetic states in newly published research

September 18, 2017 by Laura Millsaps, Ames Laboratory

Credit: Ames Laboratory

Ames Laboratory scientists have found new insight to the "rules" of how magnetic states emerge and are suppressed, creating a guide for discovery of other materials with superconducting capabilities. The discovery was made through the study of the transition metal compound LaCrGe3 under temperature, pressure, and magnetic field changes.

These findings are in a newly published paper in Nature Communications Materials and are part of Ames Laboratory's broader scope of condensed matter research dedicated to discovering new and novel states of magnetism.

"If we find transition metal-based systems with some sort of magnetism and suppress it to lower and lower temperatures, sometimes new states like superconductivity pop up, and that's what we hope for," said Paul Canfield, a senior scientist at Ames Laboratory and a Distinguished Professor and the Robert Allen Wright Professor of Physics and Astronomy at Iowa State University.In the case of LaCrGe3 the ferromagnetism is suppressed and, for certain pressures and fields, new antiferromagnetic states emerge. "By studying how magnetism is suppressed," said Canfield "we are beginning to learn some of the rules for when superconductivity, or other novel states, appear and when they don't."

Explore further: Making ferromagnets stronger by adding non-magnetic elements

More information: Udhara S. Kaluarachchi et al. Tricritical wings and modulated magnetic phases in LaCrGe3 under pressure, Nature Communications (2017). DOI: 10.1038/s41467-017-00699-x

https://phys.org/news/2017-09-physicists-magnetic-states-newly-published.html

Contact: Ariana Tantillo, (631) 344-2347, or Peter Genzer, (631) 344-3174share:
Bringing a Hidden Superconducting State to Light

High-power light reveals the existence of superconductivity associated with charge "stripes" in the copper-oxygen planes of a layered material above the temperature at which it begins to transmit electricity without resistance

February 16, 2018

Physicist Genda Gu holds a single-crystal rod of LBCO—a compound made of lanthanum, barium, copper, and oxygen—in Brookhaven's state-of-the-art crystal growth lab. The infrared image furnace he used to synthesize these high-quality crystals is pictured in the background.

UPTON, NY—A team of scientists has detected a hidden state of electronic order in a layered material containing lanthanum, barium, copper, and oxygen (LBCO). When cooled to a certain temperature and with certain concentrations of barium, LBCO is known to conduct electricity without resistance, but now there is evidence that a superconducting state actually occurs above this temperature too. It was just a matter of using the right tool—in this case, high-intensity pulses of infrared light—to be able to see it.

Reported in a paper published in the Feb. 2 issue of Science, the team’s finding provides further insight into the decades-long mystery of superconductivity in LBCO and similar compounds containing copper and oxygen layers sandwiched between other elements. These “cuprates” become superconducting at relatively higher temperatures than traditional superconductors, which must be frozen to near absolute zero (minus 459 degrees Fahrenheit) before their electrons can flow through them at 100-percent efficiency. Understanding why cuprates behave the way they do could help scientists design better high-temperature superconductors, eliminating the cost of expensive cooling systems and improving the efficiency of power generation, transmission, and distribution. Imagine computers that never heat up and power grids that never lose energy.

“The ultimate goal is to achieve superconductivity at room temperature,” said John Tranquada, a physicist and leader of the Neutron Scatter Group in the Condensed Matter Physics and Materials Science Department at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory, where he has been studying cuprates since the 1980s. “If we want to do that by design, we have to figure out which features are essential for superconductivity. Teasing out those features in such complicated materials as the cuprates is no easy task.”

The copper-oxygen planes of LBCO contain “stripes” of electrical charge separated by a type of magnetism in which the electron spins alternate in opposite directions. In order for LBCO to become superconducting, the individual electrons in these stripes need to be able to pair up and move in unison throughout the material.

Previous experiments showed that, above the temperature at which LBCO becomes superconducting, resistance occurs when the electrical transport is perpendicular to the planes but is zero when the transport is parallel. Theorists proposed that this phenomenon might be the consequence of an unusual spatial modulation of the superconductivity, with the amplitude of the superconducting state oscillating from positive to negative on moving from one charge stripe to the next. The stripe pattern rotates by 90 degrees from layer to layer, and they thought that this relative orientation was blocking the superconducting electron pairs from moving coherently between the layers.

“This idea is similar to passing light through a pair of optical polarizers, such as the lenses of certain sunglasses,” said Tranquada. “When the polarizers have the same orientation, they pass light, but when their relative orientation is rotated to 90 degrees, they block all light.”

However, a direct experimental test of this picture had been lacking—until now.

One of the challenges is synthesizing the large, high-quality single crystals of LBCO needed to conduct experiments. “It takes two months to grow one crystal, and the process requires precise control over temperature, atmosphere, chemical composition, and other conditions,” said co-author Genda Gu, a physicist in Tranquada’s group. Gu used an infrared image furnace—a machine with two bright lamps that focus infrared light onto a cylindrical rod containing the starting material, heating it to nearly 2500 degrees Fahrenheit and causing it to melt—in his crystal growth lab to grow the LBCO crystals.

Collaborators at the Max Planck Institute for the Structure and Dynamics of Matter and the University of Oxford then directed infrared light, generated from high-intensity laser pulses, at the crystals (with the light polarization in a direction perpendicular to the planes) and measured the intensity of light reflected back from the sample. Besides the usual response—the crystals reflected the same frequency of light that was sent in—the scientists detected a signal three times higher than the frequency of that incident light.

“For samples with three-dimensional superconductivity, the superconducting signature can be seen at both the fundamental frequency and at the third harmonic,” said Tranquada. “For a sample in which charge stripes block the superconducting current between layers, there is no optical signature at the fundamental frequency. However, by driving the system out of equilibrium with the intense infrared light, the scientists induced a net coupling between the layers, and the superconducting signature shows up in the third harmonic. We had suspected that the electron pairing was present—it just required a stronger tool to bring this superconductivity to light.”

(more at link...)
https://www.bnl.gov/newsroom/news.php?a=112737

Cuprate Superconductors

Schematic phase diagram of a hole doped cuprate superconductor and crystal structure of CuO2 planes

High-transition-temperature (Tc) superconductivity in copper oxides (cuprates) is one of the most intriguing emergent phenomena in strongly correlated electron systems. It has attracted great attention since its discovery because Tc can exceed the boiling temperature of liquid nitrogen, which is much higher than the putative limit of Tc ~ 40 K derived from the BCS theory for conventional superconductivity.

The cuprate superconductors have a layered crystal structure consisting of CuO2 planes separated by charge reservoir layers, which may dope electrons or holes into the CuO2 planes. On doping holes, the antiferromagnetic Mott insulating phase of the parent compounds disappears and superconductivity emerges. Tc follows a dome-like shape as a function of doping, with a maximum Tc around 16% doped per CuO2 plaquette. A similar phase diagram is seen on doping electrons, albeit with a more robust antiferromagnetic phase and a lower Tc. On the hole-doped side, there exists an enigmatic state above Tc called the pseudogap, where the electron density of states within certain momentum region is suppressed.

https://arpes.stanford.edu/research/quantum-materials/cuprate-superconductors

....

Viewpoint: Cuprate Superconductors May Be Conventional After All

   Can-Li Song, Department of Physics, Tsinghua University, Beijing 100084, China
   Qi-Kun Xue, Department of Physics, Tsinghua University, Beijing 100084, China

December 4, 2017• Physics 10, 129
Experiments on a copper-based high-temperature superconductor uncover the existence of vortex states—a hallmark of conventional superconductivity.

APS/Alan Stonebraker
Figure 1: Bardeen-Cooper-Schrieffer theory predicts that vortex states are formed in conventional type-II superconductors in a magnetic field. Renner and co-workers have observed such states in the high-Tc cuprate YBa2Cu3O7−

Renner and colleagues’ experiment shows that applying a magnetic field to Y123 produces vortex states similar to those seen in conventional type-II BCS superconductors. While this result doesn’t yet tell us why copper oxides exhibit superconductivity at such high temperatures, it strongly suggests that superconductivity in copper oxides may be of the conventional BCS type. This conclusion is consistent with recent studies, which showed that several types of high- Tc superconductors—including monolayer FeSe films ( Tc>65K) [8] and pressurized H2S ( Tc=203K) [9]—can also be described by BCS theory. Within this context, the work of Renner’s group may signal that we are getting close to the discovery of a unifying mechanism for high- Tc superconductivity.

Several caveats about this work, however, are worth mentioning. First, the simple hypothesis of an additive tunneling conductance from SC and NSC channels might be questionable: The electrons in the SC channel may interact with those in other channels, complicating the interpretation of the measurements. Further experiments in other materials where the NSC channel has been well characterized will show whether the assumption is justified. Second, the samples may be in a “dirty” regime (in which the mean-free path of electrons is shorter than the coherence length of superconducting Cooper pairs). In such a regime, the vortices do not host bound states, but the subtraction process could lead to signals that could be misinterpreted as the ZBCPs associated with vortex states. Ruling out this possibility would require a quantification of the ZBCP amplitudes. Finally, the vortices measured by the authors exhibit an unexpected variability in their ZBCP spectra: for some vortices the ZBCP splits into a double peak when measured away from the vortex centers, whereas for others it does not. The authors attribute such variability to effects of disorder in the lattice of vortices. Experiments using cleaner samples will be necessary to confirm this interpretation.

...

Iridates and cuprate superconductors: the similarities are more than skin deep
July 11, 2014

https://physics.aps.org/articles/pdf/10.1103/Physics.10.129

https://dash.harvard.edu/handle/1/17465318


So far, the superconductivity community has documented that cuprates have certain characteristics that seem to set them apart and provide a ‘recipe’ for high-temperature superconductivity: their copper atoms sit in a two-dimensional square lattice, have a spin-½ ion, and “talk” to each other magnetically through a phenomenon known as Heisenberg exchange.

The thought goes that if other materials share these characteristics, they could be undiscovered superconductors—or if they are missing just one or two ingredients, they could provide clues to how cuprate superconductivity works. (Studying systems that are very similar, but with one ingredient missing, is a classic scientific technique).

An international Argonne-led team decided to try their luck with iridium oxides. These, it turns out, have all three characteristics—they are built up of spin-½ ions on a two-dimensional grid structure, and the ions follow the expectations of Heisenberg exchange behavior—but no one has observed superconductivity in them. Yet. The reason is that most cuprates need to have mobile charges in the form of extra electrons or holes added in a process called doping before they become superconducting, and iridates have been very resistant to this process.

B.J. Kim, one of the Argonne authors, thought to add potassium ions to the surface as a way of providing these charges. As he measured the electronic structure, he found that a very thin top layer of the iridate started to behave as though it were doped into a metallic state, the same kind of doping needed for cuprate superconductors. More importantly, Kim found the doped iridate shared a key electronic structure found in the cuprates—a Fermi arc that evolved into a closed Fermi surface as he added more potassium ions or warmed the sample.

Although they did not find evidence for superconductivity, the team plans to continue exploring this material and related iridium oxides.

“The work is an existence proof that these very special Fermi arcs can be found in materials other than cuprates—which could itself suggest that the family of superconductors could be much larger than currently known,” said Argonne scientist John Mitchell, one of the coauthors of the study. “It will also make us look very carefully at how these arcs may or may not result from the same underlying physics as the cuprates.”

...

Here are the base elements of CaKFe4As4. How to get the N-S going in one direction only with the molecule :

.
Cr6, I believe you’re asking for a suggested configuration for a superconducting molecule, CaKFe4As4.

All those double alphas - which I think makes Fe such a good two-way conductor - make all four elements very self-similar. What is the superconducting definition? It could be as simple as aligning the molecule properly on a tabletop.

The first configuration that springs into mind is the single file filament, but that makes no sense to me at all.
Four As in a square configuration, (the south layer), each topped with an Fe (the north layer). The north pole position might be K and the south pole Ca.


Nevyn, I see you’re at Atomic Viewer 0.9. I know you’ve built plenty of molecules. Can users build molecules?
.

Here's my proposed alignment. Iron and Arsenic are the work horses. They have all of those protons in their centers that can take a lot of charge and they are very balanced in the carousel levels. Potassium and Calcium are going to be the top and bottom atoms because they don't have carousel protons.

Iron will sit on top of Arsenic with the single hook proton of Arsenic bonding with the 2 hook protons on the bottom of Iron. That gives us a very balanced molecule with 3 protons bonding them together. This creates an increased potential for charge flow through both of them.

Potassium and Calcium are very similar to each other with the only difference being an extra proton on the bottom of Calcium. We want a balanced molecule so we put Potassium on top of Iron and Calcium underneath Arsenic. This gives us a 3 proton bond between Calcium and Arsenic to match the 3 proton bond between Arsenic and Iron, keeping a smooth flow through the internals. The bond between Potassium and Calcium is not quite as strong as it only contains 2 protons. This may mean that there is a slight difference between photon flow and anti-photon flow, but not much.

We actually have 4 Iron and 4 Arsenic atoms to play with and we just stack them in FeAr pairs, always leaving K and Ca as the intake/exhaust ports. This does create some bonds between Fe and Ar that contains 4 protons but this just boosts the charge potential even further. These bonds will never operate at their full potential because the rest of the molecule can not pull in that amount of charge.

How does it work?

Iron will usually create magnetic fields because it is quite balanced and has a large carousel level. Not quite as much for Arsenic because it has a differential from top to bottom which indicates an increase in through-charge rather than magnetic charge. This is a good thing because we want through-charge and minimal magnetic charge. Arsenic will essentially convert Iron into a better conductor. Potassium and Calcium do not have carousel levels so they are already good for through-charge. This gives us a nice straight path through the molecule with minimal carousel interaction. Those carousel levels are not useless though. They do still emit some charge which is used to protect the internal through-charge stream from outside influence.

That analysis assumed no funky proton re-arrangements like Miles describes for Neodymium. I admit that I get a bit lost in the possibilities when I think about that. I don't think it is necessary here but it may play some part.

I tried to create an image of this molecule but I don't have the usual software that I use and GIMP is being a little bitch (translation: I don't understand how to use it and don't have the time to figure it out right now). I could use my old desktop Atomic Viewer to put them together but it takes too much time to get all of the bonds aligned.

No, web-based AV can not build molecules yet. That might be my big project for this year. No promises because I haven't felt the desire to dive back in to any of this lately but I'm sure that will change soon enough. You guys have piqued my interests a few times with some good discussions but I haven't taken that leap quite yet.

Thanks for showing the connections.

Found a few more recent articles. A few newer SC molecules are coming out:

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Graphene's sleeping superconductivity awakens
January 19, 2017, University of Cambridge
graphene
Credit: AlexanderAlUS/Wikipedia/CC BY-SA 3.0

(more at link... https://phys.org/news/2017-01-graphene-superconductivity-awakens.html )

Researchers have found a way to trigger the innate, but previously hidden, ability of graphene to act as a superconductor - meaning that it can be made to carry an electrical current with zero resistance.

The finding, reported in Nature Communications, further enhances the potential of graphene, which is already widely seen as a material that could revolutionise industries such as healthcare and electronics. Graphene is a two-dimensional sheet of carbon atoms and combines several remarkable properties; for example, it is very strong, but also light and flexible, and highly conductive.

Since its discovery in 2004, scientists have speculated that graphene may also have the capacity to be a superconductor. Until now, superconductivity in graphene has only been achieved by doping it with, or by placing it on, a superconducting material - a process which can compromise some of its other properties.

But in the new study, researchers at the University of Cambridge managed to activate the dormant potential for graphene to superconduct in its own right. This was achieved by coupling it with a material called praseodymium cerium copper oxide (PCCO).

Superconductors are already used in numerous applications. Because they generate large magnetic fields they are an essential component in MRI scanners and levitating trains. They could also be used to make energy-efficient power lines and devices capable of storing energy for millions of years.

Superconducting graphene opens up yet more possibilities. The researchers suggest, for example, that graphene could now be used to create new types of superconducting quantum devices for high-speed computing. Intriguingly, it might also be used to prove the existence of a mysterious form of superconductivity known as "p-wave" superconductivity, which academics have been struggling to verify for more than 20 years.

The research was led by Dr Angelo Di Bernardo and Dr Jason Robinson, Fellows at St John's College, University of Cambridge, alongside collaborators Professor Andrea Ferrari, from the Cambridge Graphene Centre; Professor Oded Millo, from the Hebrew University of Jerusalem, and Professor Jacob Linder, at the Norwegian University of Science and Technology in Trondheim.

"It has long been postulated that, under the right conditions, graphene should undergo a superconducting transition, but can't," Robinson said. "The idea of this experiment was, if we couple graphene to a superconductor, can we switch that intrinsic superconductivity on? The question then becomes how do you know that the superconductivity you are seeing is coming from within the graphene itself, and not the underlying superconductor?"

Similar approaches have been taken in previous studies using metallic-based superconductors, but with limited success. "Placing graphene on a metal can dramatically alter the properties so it is technically no longer behaving as we would expect," Di Bernardo said. "What you see is not graphene's intrinsic superconductivity, but simply that of the underlying superconductor being passed on."

PCCO is an oxide from a wider class of superconducting materials called "cuprates". It also has well-understood electronic properties, and using a technique called scanning and tunnelling microscopy, the researchers were able to distinguish the superconductivity in PCCO from the superconductivity observed in graphene.

Superconductivity is characterised by the way the electrons interact: within a superconductor electrons form pairs, and the spin alignment between the electrons of a pair may be different depending on the type - or "symmetry" - of superconductivity involved. In PCCO, for example, the pairs' spin state is misaligned (antiparallel), in what is known as a "d-wave state".

By contrast, when graphene was coupled to superconducting PCCO in the Cambridge-led experiment, the results suggested that the electron pairs within graphene were in a p-wave state. "What we saw in the graphene was, in other words, a very different type of superconductivity than in PCCO," Robinson said. "This was a really important step because it meant that we knew the superconductivity was not coming from outside it and that the PCCO was therefore only required to unleash the intrinsic superconductivity of graphene."

It remains unclear what type of superconductivity the team activated, but their results strongly indicate that it is the elusive "p-wave" form. If so, the study could transform the ongoing debate about whether this mysterious type of superconductivity exists, and - if so - what exactly it is.

In 1994, researchers in Japan fabricated a triplet superconductor that may have a p-wave symmetry using a material called strontium ruthenate (SRO). The p-wave symmetry of SRO has never been fully verified, partly hindered by the fact that SRO is a bulky crystal, which makes it challenging to fabricate into the type of devices necessary to test theoretical predictions.

https://phys.org/news/2017-01-graphene-superconductivity-awakens.html

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A different spin on superconductivity—Unusual particle interactions open up new possibilities in exotic materials
April 7, 2018, University of Maryland
(more at link...
https://phys.org/news/2018-04-superconductivityunusual-particle-interactions-possibilities-exotic.html
)

When you plug in an appliance or flip on a light switch, electricity seems to flow instantly through wires in the wall. But in fact, the electricity is carried by tiny particles called electrons that slowly drift through the wires. On their journey, electrons occasionally bump into the material's atoms, giving up some energy with every collision.

The degree to which electrons travel unhindered determines how well a material can conduct electricity. Environmental changes can enhance conductivity, in some cases drastically. For example, when certain materials are cooled to frigid temperatures, electrons team up so they can flow uninhibited, without losing any energy at all—a phenomenon called superconductivity.

Now a team of researchers from the University of Maryland (UMD) Department of Physics together with collaborators has seen exotic superconductivity that relies on highly unusual electron interactions. While predicted to occur in other non-material systems, this type of behavior has remained elusive. The team's research, published in the April 6 issue of Science Advances, reveals effects that are profoundly different from anything that has been seen before with superconductivity.

Electron interactions in superconductors are dictated by a quantum property called spin. In an ordinary superconductor, electrons, which carry a spin of ½, pair up and flow uninhibited with the help of vibrations in the atomic structure. This theory is well-tested and can describe the behavior of most superconductors. In this new research, the team uncovers evidence for a new type of superconductivity in the material YPtBi, one that seems to arise from spin-3/2 particles.

"No one had really thought that this was possible in solid materials," explains Johnpierre Paglione, a UMD physics professor and senior author on the study. "High-spin states in individual atoms are possible but once you put the atoms together in a solid, these states usually break apart and you end up with spin one-half. "

Finding that YPtBi was a superconductor surprised the researchers in the first place. Most superconductors start out as reasonably good conductors, with a lot of mobile electrons—an ingredient that YPtBi is lacking. According to the conventional theory, YPtBi would need about a thousand times more mobile electrons in order to become superconducting at temperatures below 0.8 Kelvin. And yet, upon cooling the material to this temperature, the team saw superconductivity happen anyway. This was a first sign that something exotic was going on inside this material.

After discovering the anomalous superconducting transition, researchers made measurements that gave them insight into the underlying electron pairing. They studied a telling feature of superconductors—their interaction with magnetic fields. As the material undergoes the transition to a superconductor, it will try to expel any added magnetic field from its interior. But the expulsion is not completely perfect. Near the surface, the magnetic field can still enter the material but then quickly decays away. How far it goes in depends on the nature of the electron pairing, and changes as the material is cooled down further and further.

To probe this effect, the researchers varied the temperature in a small sample of the material while exposing it to a magnetic field more than ten times weaker than the Earth's. A copper coil surrounding the sample detected changes to the superconductor's magnetic properties and allowed the team to sensitively measure tiny variations in how deep the magnetic field reached inside the superconductor.

The measurement revealed an unusual magnetic intrusion. As the material warmed from absolute zero, the field penetration depth for YPtBi increased linearly instead of exponentially as it would for a conventional superconductor. This effect, combined with other measurements and theory calculations, constrained the possible ways that electrons could pair up. The researchers concluded that the best explanation for the superconductivity was electrons disguised as particles with a higher spin—a possibility that hadn't even been considered before in the framework of conventional superconductivity.

The discovery of this high-spin superconductor has given a new direction for this research field. "We used to be confined to pairing with spin one-half particles," says Hyunsoo Kim, lead author and a UMD assistant research scientist. "But if we start considering higher spin, then the landscape of this superconducting research expands and just gets more interesting."

Looks like YPtBi is at a higher stack level overall but the same mix of Charge is at play. "Y" couldn't resolve in the browser with Nevyn's Periodic table so I used Nb. Again the key question is how these molecules bond with each other to create a N-S or other strong (non-magnetic per Nevyn) directional flow? Always remember that Nb makes the strongest natural magnets:

https://www.nevyns-lab.com/mathis/app/AtomicViewer/AtomicViewer.php

We are going to have to use Nevyn's Periodic Table to diagram each of these Superconducting molecules/materials. I bet a definitive "form" will come out showing the binding for better determination (and perhaps even prediction?) to indicate what actually creates a superconductor since official theory at a complete loss apparently.

The higher elements have not been added to AV because they are very large and the possible changes from one element in the table to the next (i.e. how to add the next proton) are difficult to choose between. If anyone finds evidence for these elements bonding to other elements, hopefully known ones, then I might be able to create a few more.

I've been thinking about how to start a Molecular Builder. I'm trying a few different ideas, just in my head at the moment, on how to build a molecule. There always seems to be something that makes each approach unusable for some scenario. The main problem is complex structures like rings. They require special handling as they sometimes need to bend the atoms themselves. I'm thinking about ignoring them for now and just getting something working. I could make something to handle the types of structures that are being discussed here. Most cases seem easy enough but I want to create a framework that can work for most, if not all, cases.

I wouldn't hold my breath waiting for it though. It will still take me some time to get something that is operational.

The best approach I have come up with so far requires the user to select the bond type before the atoms. The bond will be rendered in some way so that the user can see where to attach atoms to it. The atoms will then be aligned and rendered. While in building mode, you will be able to see all bonds which will, hopefully, look like mechanical linkages. Jared, if you're interested, maybe you could help me with some 3D models for the bonds. You are certainly more graphically artistic than I am. When not in build mode, the bonds will not be visible and the atoms will move closer together, more like an actual bond between elements.

I initially wanted a more free-flowing system where the user could drop atoms in and drag them around. The system would look for potential bond points that were near the atom being moved and if dropped near one of them, it would create the bond. The more I thought about it though, the more difficult it looked.

I think the Bond-First approach will be easier than the Drag'n'Drop system. In the very least, it will be easier to start with and I might see other ways as I develop that. I sometimes have to remind myself that I don't need to solve all problems in the first go.

Totally agree Nevyn... it can get very complex quickly with charge flow replications of classical "bonding".

The electron.pdf is really good for looking at this. He puts a whole slew of new requirements for the flows with (positrons versus the electron):
...
(Mathis)
In fact, we now have strong experimental evidence I am correct. Ultra-intense lasers have been used to irradiate a gold target, producing very large numbers of positrons. There is no indication of beta decay or the weak force in this phenomenon. Rather, it appears to me that the energy of the laser is able to knock positrons directly out of the south poles of the gold nuclei. Properly aimed, the laser may even be knocking positrons out of other positions as well, including positions in the carousel level. Because hundreds of billions of positrons are produced this way—not just a few—it strongly indicates the positrons were in the gold nuclei to start with.

I remind my readers of several things at this juncture. It is known that positrons are created in
radioactive decay, but currently they are said to be created by invoking the weak force (mainly in beta decay). I have shown you this is completely ad hoc as well as unnecessary. If they are already in the nucleus, their appearance in decay doesn't have to be explained as a creation by some new-fangled process. They aren't created, they are simply freed from the south pole and other normal locations in the nucleus. And, as we will see below, in most cases, the leptons “produced” in decay aren't ionized at all. They aren't freed from the nucleus at all. They are free both before and after the decay.
...
I will be told that in most cases, Argon is produced here by electron capture. Only rarely is Argon
produced by positron emission. Yes, but notice that electron capture and positron emission are almost the same thing. The electron and positron are opposite, and the words capture and emission are opposite. So, what we are seeing is not that the positron emission happens less often, but that it is harder for us to detect. It is hard for us to detect the positron leaving the site of this impact, so we simply assume it usually isn't happening. But it is always happening. Only a fraction of the time will we be able to detect the positron leaving. Why? Because in leaving, it overwrites the track of the incoming electron. Since we detect these particles by the tracks they leave, if it overwrites the electron track perfectly, we can't detect it. This means there is no such thing as either electron capture or positron emission (during beta decay). All these events are collisions, not captures or emissions.

Some superconductors can also carry currents of 'spin'
April 16, 2018, University of Cambridge

Conceptual image of spin current flow in a superconductor. Credit: Jason Robinson

Researchers have shown that certain superconductors—materials that carry electrical current with zero resistance at very low temperatures—can also carry currents of 'spin'. The successful combination of superconductivity and spin could lead to a revolution in high-performance computing, by dramatically reducing energy consumption.

Spin is a particle's intrinsic angular momentum, and is normally carried in non-superconducting, non-magnetic materials by individual electrons. Spin can be 'up' or 'down', and for any given material, there is a maximum length that spin can be carried. In a conventional superconductor electrons with opposite spins are paired together so that a flow of electrons carries zero spin.

A few years ago, researchers from the University of Cambridge showed that it was possible to create electron pairs in which the spins are aligned: up-up or down-down. The spin current can be carried by up-up and down-down pairs moving in opposite directions with a net charge current of zero. The ability to create such a pure spin supercurrent is an important step towards the team's vision of creating a superconducting computing technology which could use massively less energy than the present silicon-based electronics.

Now, the same researchers have found a set of materials which encourage the pairing of spin-aligned electrons, so that a spin current flows more effectively in the superconducting state than in the non-superconducting (normal) state. Their results are reported in the journal Nature Materials.

"Although some aspects of normal state spin electronics, or spintronics, are more efficient than standard semiconductor electronics, the large-scale application has been prevented because the large charge currents required to generate spin currents waste too much energy," said Professor Mark Blamire of Cambridge's Department of Materials Science and Metallurgy, who led the research. "A fully-superconducting method of generating and controlling spin currents offers a way to improve on this."

In the current work, Blamire and his collaborators used a multi-layered stack of metal films in which each layer was only a few nanometres thick. They observed that when a microwave field was applied to the films, it caused the central magnetic layer to emit a spin current into the superconductor next to it.

(more at link... https://phys.org/news/2018-04-superconductors-currents.html#nRlv )
....

https://phys.org/news/2015-06-efficient-conversion-currents-superconductor.html


Graphene single photon detectors
September 6, 2017, ICFO
https://phys.org/news/2017-09-graphene-photon-detectors.html

Current detectors are efficient at detecting incoming photons that have relatively high energies, but their sensitivity drastically decreases for low frequency, low energy photons. In recent years, graphene has shown to be an exceptionally efficient photo-detector for a wide range of the electromagnetic spectrum, enabling new types of applications for this field.

Thus, in a recent paper published in the journal Physical Review Applied, and highlighted in APS Physics, ICFO researcher and group leader Prof. Dmitri Efetov, in collaboration with researchers from Harvard University, MIT, Raytheon BBN Technologies and Pohang University of Science and Technology, have proposed the use of graphene-based Josephson junctions (GJJs) to detect single photons in a wide electromagnetic spectrum, ranging from the visible down to the low end of radio frequencies, in the gigahertz range.

Light may unlock a new quantum dance for electrons in graphene
January 15, 2018 by Nina Beier, Joint Quantum Institute


Electrons carry out this choreography—known as the fractional quantum Hall effect—in graphene. Interestingly, tuning the interactions between electrons can coax them into different quantum Hall dance patterns, but it requires a stronger magnet or an entirely different sample—sometimes with two layers of graphene stacked together.

The new work, which is a collaboration between researchers at JQI and the City College of New York, proposes using laser light to circumvent some of these experimental challenges and even create novel quantum dances. The light can prod electrons into jumping between orbits of different energies. As a result, the interactions between the electrons change and lead to a different dance pattern, including some that have never been seen before in experiments. The intensity and frequency of the light alter the number of electrons in specific orbits, providing an easy way to control the electrons' performance. "Such a light-matter interaction results in some models that have previously been studied theoretically," says Mohammad Hafezi, a JQI Fellow and an author of the paper. "But no experimental scheme was proposed to implement them."

Unlocking those theoretical dances may reveal novel quantum behavior. Some may even spawn exotic quantum particles that could collaborate to remain protected from noise—a tantalizing idea that could be useful in the quest to build robust quantum computers.

https://phys.org/news/2018-01-quantum-electrons-graphene.html