Partial List of Superconductors to Build Out

Page 2 of 2 Previous  1, 2

Go down

Re: Partial List of Superconductors to Build Out

Post by Nevyn on Wed May 16, 2018 2:40 am

All of these are open for discussion. They are just my quick guesses. I'm looking at the bonds and deciding if the number of protons is OK and trying to keep lo-hi-lo numbers across the chain. The outer stacks I try to make unbalanced, but am not too concerned if they are not.
avatar
Nevyn
Admin

Posts : 1134
Join date : 2014-09-11

View user profile http://www.nevyns-lab.com

Back to top Go down

Re: Partial List of Superconductors to Build Out

Post by Cr6 on Fri May 25, 2018 2:24 am

Quick plug on Graphene:
...........
Rare element to provide better material for high-speed electronics
May 24, 2018 by Kayla Wiles, Purdue University


Read more at: https://phys.org/news/2018-05-rare-element-material-high-speed-electronics.html#jCp

Purdue researchers have discovered a new two-dimensional material, derived from the rare element tellurium, to make transistors that carry a current better throughout a computer chip.

The discovery adds to a list of extremely thin, two-dimensional materials that engineers have tried to use for improving the operation speed of a chip's transistors, which then allows information to be processed faster in electronic devices, such as phones and computers, and defense technologies like infrared sensors.

Other two-dimensional materials, such as graphene, black phosphorus and silicene, have lacked either stability at room temperature or the feasible production approaches required to nanomanufacture effective transistors for higher speed devices.

"All transistors need to send a large current, which translates to high-speed electronics," said Peide Ye, Purdue's Richard J. and Mary Jo Schwartz Professor of Electrical and Computer Engineering. "One-dimensional wires that currently make up transistors have very small cross sections. But a two-dimensional material, acting like a sheet, can send a current over a wider surface area."

Tellurene, a two-dimensional film researchers found in the element tellurium, achieves a stable, sheet-like transistor structure with faster-moving "carriers—meaning electrons and the holes they leave in their place. Despite tellurium's rarity, the pros of tellurene would make transistors made from two-dimensional materials easier to produce on a larger scale. The researchers detail their findings in Nature Electronics.


Read more at: https://phys.org/news/2018-05-rare-element-material-high-speed-electronics.html#jCp

https://phys.org/news/2018-05-rare-element-material-high-speed-electronics.html#nRlv

...........

One-atom-thick sheets of carbon—known as graphene—have a range of electronic properties that scientists are investigating for potential use in novel devices. Graphene's optical properties are also garnering attention, which may increase further as a result of research from the A*STAR Institute of Materials Research and Engineering (IMRE). Bing Wang of the IMRE and his co-workers have demonstrated that the interactions of single graphene sheets in certain arrays allow efficient control of light at the nanoscale.

Light squeezed between single graphene sheets can propagate more efficiently than along a single sheet. Wang notes this could have important applications in optical-nanofocusing and in superlens imaging of nanoscale objects. In conventional optical instruments, light can be controlled only by structures that are about the same scale as its wavelength, which for optical light is much greater than the thickness of graphene. By utilizing surface plasmons, which are collective movements of electrons at the surface of electrical conductors such as graphene, scientists can focus light to the size of only a few nanometers.

Wang and his co-workers calculated the theoretical propagation of surface plasmons in structures consisting of single-atomic sheets of graphene, separated by an insulating material. For small separations of around 20 nanometers, they found that the surface plasmons in the graphene sheets interacted such that they became 'coupled' (see image). This theoretical coupling was very strong, unlike that found in other materials, and greatly influenced the propagation of light between the graphene sheets.



Read more at: https://phys.org/news/2012-12-theoretical-numerical-graphene-sheets-reveals.html#jCp

Cr6
Admin

Posts : 1033
Join date : 2014-08-09

View user profile http://milesmathis.forumotion.com

Back to top Go down

Re: Partial List of Superconductors to Build Out

Post by Cr6 on Mon May 28, 2018 2:02 am

"Nematicity" is a focus with Superconductors. MBE might be a worth a lengthy investigation with the C.F.:
----------
LaBaCa2Cu4O

https://www.nevyns-lab.com/mathis/app/mbl/mbl.html?mbl=LaBaCa2Cu4O8&align=X
----------------
Background:
https://en.wikipedia.org/wiki/Epitaxially
https://en.wikipedia.org/wiki/Molecular_beam_epitaxy
----------------
https://experts.umn.edu/en/publications/what-drives-nematic-order-in-iron-based-superconductors (more at link...)

What drives nematic order in iron-based superconductors?


R. M. Fernandes, A. V. Chubukov, J. Schmalian


Abstract


Although the existence of nematic order in iron-based superconductors is now a well-established experimental fact, its origin remains controversial. Nematic order breaks the discrete lattice rotational symmetry by making the x and y directions in the iron plane non-equivalent. This can happen because of a regular structural transition or as the result of an electronically driven instability-in particular, orbital order or spin-driven Ising-nematic order. The latter is a magnetic state that breaks rotational symmetry but preserves time-reversal symmetry. Symmetry dictates that the development of one of these orders immediately induces the other two, making the origin of nematicity a physics realization of the 'chicken and egg problem'. In this Review, we argue that the evidence strongly points to an electronic mechanism of nematicity, placing nematic order in the class of correlation-driven electronic instabilities, like superconductivity and density-wave transitions. We discuss different microscopic models for nematicity and link them to the properties of the magnetic and superconducting states, providing a unified perspective on the phase diagram of the iron pnictides.

----

Electronic nematicity in a cuprate superconductor and beyond

Monday, October 2, 2017 - 2:30pm

Over the course of extensive experimental studies of La2-xSrxCuO4 films synthesized by molecular beam epitaxy, we discovered that a spontaneous voltage develops across the sample, transverse to the electrical current. This unusual metallic state, in which the rotational symmetry of the electron fluid is spontaneously broken, occurs in a large temperature and doping region. The superconducting state always emerges out of this nematic metal state. I will also present our results in searching for electronic nematicity in other oxides, implying it may be pervasive among strongly-correlated materials.

http://physics.berkeley.edu/news-events/events/20171002/electronic-nematicity-in-a-cuprate-superconductor-and-beyond

https://www.nextbigfuture.com/2016/02/electronic-nematicity-as-universal.html

---------
Scientists use soft x-ray scattering in superconductivity research

The scientists used a novel technique called soft x-ray scattering at the Canadian Light Source synchrotron in Saskatoon to probe electron scattering in specific layers in the cuprate crystalline structure. Specifically, they looked at the individual cuprate (CuO2) planes where electronic nematicity takes place, versus the crystalline distortions in between the CuO2 planes.

Electronic nematicity happens when the electron orbitals align themselves like a series of rods. The term nematicity commonly refers to when liquid crystals spontaneously align under an electric field in liquid crystal displays. In this case, the electron orbitals enter the nematic state as the temperature drops below a critical point.

Future work will tackle how electrons can be tuned for superconductivity

Although there is not yet an agreed upon explanation for why electronic nematicity occurs, it may ultimately present another knob to tune in the quest to achieve the ultimate goal of a room temperature superconductor.

“Future work will tackle how electronic nematicity can be tuned, possibly to advantage, by modifying the crystalline structure,” says Hawthorn.

Disentangling intertwined orders

In copper oxide superconductors, several types of order compete for supremacy. In addition to superconductivity, researchers have found periodic patterns in charge density (CDW order), as well as an asymmetry in the electronic density within the unit cell of some cuprates (nematicity). CDW order has been detected in the underdoped regime of all major cuprate families, but the ubiquity of nematicity is less clear. Achkar et al. used resonant x-ray scattering to find that, in the copper oxide planes of three lanthanum-based cuprates, nematicity has a temperature dependence distinct from that of a related structural distortion. This implies that there are additional, electronic mechanisms for nematicity

Abstract

In underdoped cuprate superconductors, a rich competition occurs between superconductivity and charge density wave (CDW) order. Whether rotational symmetry-breaking (nematicity) occurs intrinsically and generically or as a consequence of other orders is under debate. Here, we employ resonant x-ray scattering in stripe-ordered superconductors (La,M)2CuO4 to probe the relationship between electronic nematicity of the Cu 3d orbitals, structure of the (La,M)2O2 layers, and CDW order. We find distinct temperature dependences for the structure of the (La,M)2O2 layers and the electronic nematicity of the CuO2 planes, with only the latter being enhanced by the onset of CDW order. These results identify electronic nematicity as an order parameter that is distinct from a purely structural order parameter in underdoped striped cuprates.
https://www.nextbigfuture.com/2016/02/electronic-nematicity-as-universal.html (more at link...)

Cr6
Admin

Posts : 1033
Join date : 2014-08-09

View user profile http://milesmathis.forumotion.com

Back to top Go down

Re: Partial List of Superconductors to Build Out

Post by Cr6 on Mon May 28, 2018 2:32 am

Abrupt change of the superconducting gap structure at the nematic critical point in FeSe1−xSx

Yuki Sato, Shigeru Kasahara, Tomoya Taniguchi, Xiangzhuo Xing, Yuichi Kasahara, Yoshifumi Tokiwa, Youichi Yamakawa, Hiroshi Kontani, Takasada Shibauchi, and Yuji Matsuda

PNAS February 6, 2018. 115 (6) 1227-1231; published ahead of print January 23, 2018. https://doi.org/10.1073/pnas.1717331115

Significance

Electronic nematicity that spontaneously breaks the rotational symmetry of the underlying crystal lattice has been a growing issue in high-temperature superconductivity of iron pnictides/chalcogenides and cuprates. FeSe1 − xSx, in which the nematicity can be tuned by isoelectronic sulfur substitution, offers a fascinating opportunity to clarify the direct relationship between the nematicity and superconductivity. Here, we discover a dramatic change in the superconducting gap structure at the critical concentration of sulfur where the nematicity disappears, i.e., nematic critical point. Our observation provides direct evidence that the orbital-dependent nature of the critical nematic fluctuations has a strong impact on the superconducting pairing interaction.

http://www.pnas.org/content/115/6/1227

--------------


Nematicity, magnetism and superconductivity in FeSe

Anna E Böhmer1,3 and Andreas Kreisel2

Published 15 December 2017 • ©️ 2017 IOP Publishing Ltd
Journal of Physics: Condensed Matter, Volume 30, Number 2

Abstract


Iron-based superconductors are well known for their complex interplay between structure, magnetism and superconductivity. FeSe offers a particularly fascinating example. This material has been intensely discussed because of its extended nematic phase, whose relationship with magnetism is not obvious. Superconductivity in FeSe is highly tunable, with the superconducting transition temperature, T c, ranging from 8 K in bulk single crystals at ambient pressure to almost 40 K under pressure or in intercalated systems, and to even higher temperatures in thin films. In this topical review, we present an overview of nematicity, magnetism and superconductivity, and discuss the interplay of these phases in FeSe. We focus on bulk FeSe and the effects of physical pressure and chemical substitutions as tuning parameters. The experimental results are discussed in the context of the well-studied iron-pnictide superconductors and interpretations from theoretical approaches are presented.

http://iopscience.iop.org/article/10.1088/1361-648X/aa9caa

Cr6
Admin

Posts : 1033
Join date : 2014-08-09

View user profile http://milesmathis.forumotion.com

Back to top Go down

Re: Partial List of Superconductors to Build Out

Post by Cr6 on Mon May 28, 2018 2:43 am

This article provides pretty good background on "nematicity":
http://www.nature.com/nature/journal/v486/n7403/full/nature11178.html

BaFe2As2
https://www.nevyns-lab.com/mathis/app/mbl/mbl.html?mbl=BaFe2As2&align=Z
-------------

Asymmetry may provide clue to superconductivity


Iron-based high-temp superconductors show unexpected electronic asymmetry

HOUSTON — (June 20, 2012) — Japanese and U.S. physicists are offering new details this week in the journal Nature regarding intriguing similarities between the quirky electronic properties of a new iron-based high-temperature superconductor (HTS) and its copper-based cousins.

While investigating a recently discovered iron-based HTS, the researchers found that its electronic properties were different in the horizontal and vertical directions. This electronic asymmetry was measured across a wide range of temperatures, including those where the material is a superconductor. The asymmetry was also found in materials that were “doped” differently. Doping is a process of chemical substitution that allows both copper- and iron-based HTS materials to become superconductors.


Andriy Nevidomskyy
“The robustness of the reported asymmetric order across a wide range of chemical substitutions and temperatures is an indication that this asymmetry is an example of collective electronic behavior caused by quantum correlation between electrons,” said study co-author Andriy Nevidomskyy, assistant professor of physics at Rice University in Houston.

The study by Nevidomskyy and colleagues from Kyoto University in Kyoto, Japan, and the Japan Synchrotron Radiation Research Institute (JASRI) in Hyogo offers new clues to scientists studying the mystery of high-temperature superconductivity, one of physics’ greatest unsolved mysteries.

Superconductivity occurs when electrons form a quantum state that allows them to flow freely through a material without electrical resistance. The phenomenon only occurs at extremely cold temperatures, but two families of layered metal compounds — one based on copper and the other on iron — perform this mind-bending feat just short of or above the temperature of liquid nitrogen — negative 321 degrees Fahrenheit — an important threshold for industrial applications. Despite more than 25 years of research, scientists are still debating what causes high-temperature superconductivity.

Copper-based HTSs were discovered more than 20 years before their iron-based cousins. Both materials are layered, but they are strikingly different in other ways. For example, the undoped parent compounds of copper HTSs are nonmetallic, while their iron-based counterparts are metals. Due to these and other differences, the behavior of the two classes of HTSs are as dissimilar as they are similar — a fact that has complicated the search for answers about how high-temperature superconductivity arises.


One feature that has been found in both compounds is electronic asymmetry — properties like resistance and conductivity are different when measured up and down rather than side to side. This asymmetry, which physicists also call “nematicity,” has previously been found in both copper-based and iron-based high-temperature superconductors, and the new study provides the strongest evidence yet of electronic nematicity in HTSs.

http://news.rice.edu/2012/06/20/asymmetry-may-provide-clue-to-superconductivity/

Cr6
Admin

Posts : 1033
Join date : 2014-08-09

View user profile http://milesmathis.forumotion.com

Back to top Go down

Re: Partial List of Superconductors to Build Out

Post by Cr6 on Wed May 30, 2018 1:27 am

Looking at the S.C. LaBaCa2Cu4O8 above made me think it looked as if Hg could be swapped in as well and sure enough they have one:
HgBa2Ca3Cu4O10
https://www.nevyns-lab.com/mathis/app/mbl/mbl.html?mbl=HgBa2Ca3Cu4O10&align=X
------

In this note we report preliminary results concerning a remarkably strong phonon self- energy effect observed in HgBa2Ca3Cu4O10‡d (Hg-1234) superconductor. We measured single crystals in a Hg-1234 ceramic pellet (Tc ˆ 123 K, determined by zero resistance) prepared by a high-pressure high-temperature technique [2]. Micro-Raman scattering spectra were collected with a Dilor XY multichannel spectrometer equipped with an optical microscope in an exact backscattering geometry using the 647.1 nm laser line. The samples were kept and cooled in a continuous flow liquid helium cryostat. In Fig. 1 we present some typical Raman spectra of a large Hg-1234 grain in parallel polarization and at different temperatures. At room temperature, the absence of sharp phonon features in the 450 to 600 cmÿ1 region indicates that the grain surface is normal to the c-axis [2]. Above Tc, one can see three weak features at 240, 360 and 410 cmÿ1 superimposed on a nearly flat background, and the spectra show little change with temperature. The rather weak 240 and 360 cmÿ1 phonons exhibit strong coupling with the scattering continuum manifested by an asymmetric lineshape (Fano profile). Below Tc, a dramatic spectral change occurs: the spectral background shows a clear redistribu- tion upon entering the superconducting state and the weak phonon features strongly increase in intensity with decreasing temperature, accompanied by an abrupt change in peak position and line- width. In addition, two weak new peaks, at 480 and 570 cmÿ1, appear at low temperatures. The remarkable spectral change in Hg-1234 below Tc is clearly related to the opening of the superconducting gap and to coupled electron±phonon excitations: the piled up density of states (the electronic scattering peak) strongly modifies the phonon self-energy. Preliminary calculations show that the oscillator strength of the phonons observed below Tc is induced by the admixture of pair-breaking transitions via electron±phonon interaction. Such superconductivity-induced effects, particularly the increase in the phonon intensity, are among the strongest ones observed in the cuprate superconductors so far [3].

https://docslide.us/documents/strong-electronphonon-interactions-in-hgba2ca3cu4o10-superconductor.html

Cr6
Admin

Posts : 1033
Join date : 2014-08-09

View user profile http://milesmathis.forumotion.com

Back to top Go down

Re: Partial List of Superconductors to Build Out

Post by Cr6 on Wed May 30, 2018 1:49 am

Was thinking of these Mathis quotes and the B-Field after reading about "nematicity":
-----------
SUPERCONDUCTIVITY
In short, Copper conducts well because it channels charge efficiently from south pole to north pole. All elements normally channel from pole to equator, and Copper still channels a large percentage that way; but Copper channels more from pole to pole than any other element except Silver. To understand exactly why, you will have to read that paper, but studying Copper helps us understand what conduction is as a matter of charge channeling. Once we understand that, we can comprehend what causes superconduction.
http://milesmathis.com/conduct.html

Solid Light? No, just another bad interpretation of the Charge Field


And if you think the quantum mechanical explanation is more rigorous, you aren't paying attention.  Notice it includes an electron-phonon interaction.  There is no such beast as a phonon.  It is another fudge.  It was dreamed up to fill a hole, like the polariton and the qubit and the quasi-particle and the virtual particle.  As with all other electron bonding theory, the Cooper pair was invented by simply ignoring and inverting the standing definitions of the charge field, and selling that as  a  new  piece  of  physics.    It  was  the  hamhanded  placement  of  an  attraction  in  the  field  where  a repulsion should have existed.   It would be like placing you in front of the Sun and telling you it was dark.
...
So  if  we  wish  to  explain  superconductivity  sensibly,  we  have  to  stick  to  the  particles  we  know  are there:  the  photons,  electrons,  and  nuclei.   That  was  impossible  to  do  without  knowing  exactly what charge was, and how it was being created and transferred; since the mainstream hasn't known that, they couldn't solve these problems sensibly.  But since I now know that, explaining superconductivity is no longer that difficult.  We simply have to follow the charge streams through the nuclear structures.  Even with my general theory of charge channeling, explaining superconductivity would be nearly impossible without  diagrams  of  the  nuclei  involved,  but  I  have  also  deduced  those,  so  we  should  make  quick progress.  I have previously provided my readers with diagrams of Copper, Oxygen, Calcium, Barium, and  Mercury,  so  we  should  be  able  to  build  an  entire  ceramic  molecule,  diagramming  the  charge channels through the full structure.  Once we have understood high-temperature superconduction, we will be in a position to read the new data from Princeton in a completely different way, without needing any quasi-particles, dimers, qubits, or other mathematical tricks.

But when we are looking at what we call electrical conduction, we are looking at the stream from south pole to north.  This stream is linear, directionalized, and coherent.  If we align the poles of adjacent nuclei, we create longer lines of conduction.  As you can probably see already, this explains the Meissner Effect in superconductivity, where interior magnetic lines disappear.  We have never been given a simple mechanical explanation for that, but my diagram of Copper supplies it immediately.  If this Copper nucleus begins superconducting, that simply means that all photons being recycled are going from pole to pole.  None are being recycled out the equatorial  or  carousel  level.   As  we  know,  the  magnetic  field  lines  are  always  orthogonal  to  the electrical field lines.  Well, the electrical fields lines go with the conduction.  They run south to north here.  The magnetic field lines are then orthogonal to that and in a circle, by the old right hand rule. Well, since we have no photons being emitted out the equator in this case, we have no magnetic field being  created.   Both  the  electrical  field  and  magnetic  field  are  caused  by  the  charge  field,  and  the charge field is just the recycled photons.  Photons that are recycled from south to north in a line create the electrical field, and photons that are recycled through the carousel level create the magnetic field. So if all charge is channeled south to north as through charge, nothing is left to create the magnetic  field.  It disappears.  This disappearance is what we call the Meissner Effect.

This tells us how the magnetic field and electrical field are related at the foundational level.  Given my theory,  we  should  have  expected the  magnetic  field  to  go  to  zero  when  the  electrical  field  was  at  a maximum,  since  the  field  creation  is a  zero-sum game.   Since  the  same  charge  field  creates  both,  a maximal electrical conduction implies a zero magnetic field.  If all charge photons are being conducted, none can be left to create the magnetic field (internally).  Since all photons are spinning, the external electrical  field  will  still  have  a  potential  magnetic  component,  but  in  the  atoms  themselves,  there  is nothing that we would call a magnetic field.  Given superconduction, those internal field lines are gone. Now, if we plug an Oxygen into that Copper nucleus, we can increase conduction even more, since the Oxygen  will  plug  in  on the  pole  (see  diagram  below).  Our  recycling  engine  will  be  bigger,  having more  fans  to  pull  charge  through  (as  it  were).   And  the  added  fans  will  all  be  aligned  on  the  pole, increasing through charge.  Under normal circumstances, CuO will still recycle some of the charge out the carousel level, so we will not have superconduction.  This begs the question: how can we cause superconduction?  What would we do to maximize conduction?  Well, obviously we would minimize charge recycling on the equator.  That would force all recycling to happen on the pole.  The easiest way to do that is stop the carousel level from spinning.  If the nucleus stops spinning about its axis, we no longer have more angular momentum on the equator, and no reason for charge to recycle out that way. This  is  what  happens  with  supercold  superconduction.  But  what  happens  with  warmer superconduction?  To figure that out, we have to look at how it is created in the lab.  We need to add  Mercury, Calcium and Barium to our diagram.


http://milesmathis.com/solidlight.pdf
----------------------------------------------

98. What is "Charge"?
...
Also remember that any other proton that enters the field of our first proton will also be emitting its own B-field. These fields may interfere to some extent, but we would still expect the combined field to be more repulsive than either field taken alone. This must mean that any protons will be driven away from each other much faster than an electron will be driven away.

You will say that we still have repulsion of both the electron and the proton, but we have not brought the newly upgraded gravitational field into the mix. This field is going to cause an apparent attraction to all particles, just like the traditional field. All particles are going to appear to “fall” toward our gravitating proton, and they are all going to fall at the same rate. Standard gravity theory, so far. But let us use Einstein’s equivalence principle to reverse only our terminology. Instead of saying that all objects are falling toward our proton, we say that our proton is chasing all objects at the same rate. An acceleration in one direction is equal to an acceleration in the other direction, in a rectilinear field.

So, in order to explain both positive charge and negative charge, we only have to propose that the proton is chasing the electron fast enough to catch it, but not fast enough to catch the proton. This gives us an apparent attraction of one, and an apparent repulsion of the other.

Another way to state this is to give numbers to the two repulsions. Say the repulsion of proton by proton by the B-field causes an acceleration of 10. And say that the repulsion of electron by proton by the B-field causes an acceleration of 2. All we have to propose is that our central proton is accelerating gravitationally at a rate greater than 2 and less than 5. Anywhere in that gap, we will see repulsion of the two protons and an attraction of the electron.

That is the simple mechanical explanation of charge.

What about current in a wire? You will ask how my theory explains that. Again, quite easily. Free electrons travel at high speed in a conducting wire, or any conductor, because the B-field is moving in only one direction in that substance. The B-field acts as a river, moving the electrons along by direct contact. This B-field river can be created in any number of ways, either by having lots of radiating particles at one end of the wire and few or none at the other, or by directionalizing the B-field through the shape of the molecules in the substance. Some molecules block certain directions of the B-field, simply by getting in the way. Of course I am simplifying to a very great degree here; but I can do so since, once my fields are understood, the questions are no longer difficult. Given my method, you can answer your own questions; and they no longer look very compelling to me.

Cr6
Admin

Posts : 1033
Join date : 2014-08-09

View user profile http://milesmathis.forumotion.com

Back to top Go down

Re: Partial List of Superconductors to Build Out

Post by Cr6 on Wed May 30, 2018 2:22 am

Organic Superconductors -- they have Bechgaard salts as a close run-up but nothing really hits the mark at the moment:

https://www.nevyns-lab.com/mathis/app/mbl/mbl.html?mbl=H12C10Se4&align=X



Why study organic superconductors?

One aspect of organic superconductors such as the Bechgaard salts that makes them interesting topics of study are that the are strongly anisotropic in structure (for more information see the crystal structure section), so that their conductivity differs along the three axes by multiple orders of magnitude. This inhibits the generation of the circular currents that cause the Meissner effect, potentially significantly increasing the critical field of these materials. Furthermore, the superconducting electrons in the Bechgaard salts are believed to form with triplet spin configurations, so that both electron spins are in the same direction, and the pairs could potentially be unaffected by magnetic fields large enough to disrupt any singlet configuration Cooper pair. Therefore, organic superconductors are good candidates for being very high critical field materials, which is important in many applications of superconductors, in particular the carrying of large amounts of current, since the limiting factor in the current capacity of superconducting wires is that too much current will make a magnetic field strong enough to destroy the superconductivity.

Even if organic superconductors do not exhibit high critical fields, they are still important to study since the standard theory of superconductivity does not apply very well to them. Their unique structure causes the current to move primarily in one or two dimensions, which creates many considerations not present in metallic superconductors, and the probable existence of spin-triplet electron pairings suggest that the mechanism for superconductivity in organic superconductors is significantly different than in regular superconductors.

http://hoffman.physics.harvard.edu/materials/organic/background.php#special

-------

The Bechgaard salts are a class of charge transfer compounds in which one electron from a pair of TMTSF molecules is transferred to the anion--the resultant positive charge on the TMTSF molecules is shared throughout the structure due to the dense packing of these flat donor molecules. The negative charges are shared on the channels of anions separated from the TMTSF molecules. In addition, the size of the anion molecule chosen dictates the spacing of the TMTSF columns and thus has an effect similar to that of an applied pressure as seen on the phase diagram. In short, both the crystal structure and the geometry of the individual TMTSF molecule are critical in ensuring the charge transfer throughout the bulk sample.

Crystal Structure

Fig 2 Carbon shown in orange, selenium in yellow, potassium in blue, and fluorine in green. Figure taken from Claude, Jerome, Physics World (1998).

The crystal structure of (TMTSF)2PF6 is shown at left with the a-axis (the stacking axis with the highest conductivity) perpendicular to the plane of the image. The TMTSF and TMTTF families both exhibit this crystal structure with stacks of organic molecules separated by the columns of negatively charged anions. The organic molecules are nearly flat and aligned in a zigzag pattern down the a-axis with a slight dimerization (the molecular orbital picture described below highlights the overlap with this alternations). The small distance between one stack and the other in the b direction leads to a slight overlap in this direction and a weak 2-D character as pressure increases.

In addition, the orientation and symmetry of the anion can have a large impact on the overall properties. For the non-centrosymetric anions, those without an inversion center, such as ClO4 and FeO4, there are two relative orientations of the anions with respect to the surrounding molecules with equivalent energies. At high temperatures, we see a thermal mixture of both forms. However, at lower temperatures the structure can undergo a disorder → order transition if cooled sufficiently slowly such that all the anions are ordered in the same fashion.

Electronic Structure
Electrical Conductivity: Molecular Orbital Picture

Electrical conductivity in the Bechgaard salts arises under normal conditions because each pair of TMTSF or TMTTF molecules donates an electron to the anion acceptor. In most cases the negatively charged anion forms a closed shell and does not contribute to the overall conductivity, so current is carried by the holes created on the TMTSF or TMTTF chains, and the conductivity depends on the hole density and the complementary mobility.

http://hoffman.physics.harvard.edu/materials/organic/properties.php#crystal


---------
https://www.nevyns-lab.com/mathis/app/mbl/mbl.html?mbl=H12C10Se4&align=X

Tetramethyltetraselenafulvalene (CAS 55259-49-9)
同義語 TMTSF
アプリケーション: A compound that exhibits superconducting properties
CAS 番号: 55259-49-9
Molecular Weight: 448.04
Molecular Formula: C10H12Se4
Supplemental Information: This is classified as a Dangerous Good for transport and may be subject to additional shipping charges.
https://www.scbt.com/scbt/ja/product/tetramethyltetraselenafulvalene-55259-49-9

-----

Potential "curiosity" with a Mathis explanation:

https://www.chem.ubc.ca/far-infrared-reflectivity-bis-tetramethyltetraselenafulvalene-hexafluoroarsenate-tmtsf2asf6-throug-0

Title -- FAR-INFRARED REFLECTIVITY OF BIS-TETRAMETHYLTETRASELENAFULVALENE HEXAFLUOROARSENATE [(TMTSF)2ASF6] THROUGH THE SPIN-DENSITY-WAVE PHASE-TRANSITION
Publication Type Journal Article
Year of Publication 1987

Details on the Salt-formations:
Crystal structure of tetra-methyl-tetra-thia-fulvalenium (1S)-camphor-10-sulfonate dihydrate.
https://europepmc.org/articles/PMC4518967/

Cr6
Admin

Posts : 1033
Join date : 2014-08-09

View user profile http://milesmathis.forumotion.com

Back to top Go down

Re: Partial List of Superconductors to Build Out

Post by Cr6 on Wed May 30, 2018 2:41 am


Cr6
Admin

Posts : 1033
Join date : 2014-08-09

View user profile http://milesmathis.forumotion.com

Back to top Go down

Re: Partial List of Superconductors to Build Out

Post by Nevyn on Wed May 30, 2018 3:16 am

Here is my attempt at Acetylcholine:

Formula: NO2C7H16
MBL: H-(C{H,H})2-N{H,H}(C{H,H})3-O-C{H,H}C-O-H
URL: https://www.nevyns-lab.com/mathis/app/mbl/mbl.html?mbl=H-(C{H,H})2-N{H,H}(C{H,H})3-O-C{H,H}C-O-H&align=X&atom=nucleus




I built Choline first to see where it came from:

Formula: C5H14NO
MBL: H-(C{H,H})2-N{H,H}(C{H,H})3-O-H
URL: https://www.nevyns-lab.com/mathis/app/mbl/mbl.html?mbl=H-(C{H,H})2-N{H,H}(C{H,H})3-O-H&align=X&atom=nucleus

avatar
Nevyn
Admin

Posts : 1134
Join date : 2014-09-11

View user profile http://www.nevyns-lab.com

Back to top Go down

Re: Partial List of Superconductors to Build Out

Post by Cr6 on Wed May 30, 2018 11:54 pm

Cool (organized) pics. They look good in the MBL engine.  I was thinking of the properties of Acetylcholine...how is it so special?
------

Functions
Acetylcholine pathway.

Acetylcholine functions in both the central nervous system (CNS) and the peripheral nervous system (PNS). In the CNS, cholinergic projections from the basal forebrain to the cerebral cortex and hippocampus support the cognitive functions of those target areas. In the PNS, acetylcholine activates muscles and is a major neurotransmitter in the autonomic nervous system.

Cellular effects


Acetylcholine processing in a synapse. After release acetylcholine is broken down by the enzyme acetylcholinesterase.

Like many other biologically active substances, acetylcholine exerts its effects by binding to and activating receptors located on the surface of cells. There are two main classes of acetylcholine receptor, nicotinic and muscarinic. They are named for chemicals that can selectively activate each type of receptor without activating the other: muscarine is a compound found in the mushroom Amanita muscaria; nicotine is found in tobacco.

Nicotinic acetylcholine receptors are ligand-gated ion channels permeable to sodium, potassium, and calcium ions. In other words, they are ion channels embedded in cell membranes, capable of switching from a closed to open state when acetylcholine binds to them; in the open state they allow ions to pass through. Nicotinic receptors come in two main types, known as muscle-type and neuronal-type. The muscle-type can be selectively blocked by curare, the neuronal-type by hexamethonium. The main location of muscle-type receptors is on muscle cells, as described in more detail below. Neuronal-type receptors are located in autonomic ganglia (both sympathetic and parasympathetic), and in the central nervous system.

Is this like a para-"organic" superconductor? Are there properties that allow "nerves" to channel charge?
https://en.wikipedia.org/wiki/Neurotransmitter

https://upload.wikimedia.org/wikipedia/commons/thumb/d/d7/SynapseSchematic_lines.svg/1200px-SynapseSchematic_lines.svg.png

https://en.wikipedia.org/wiki/Choline_acetyltransferase

The muscarinic action of acetylcholine in the CNS is implicated in learning and memory. The loss of cholinergic innervation in the neocortex has been associated with memory loss, as is evidenced in advanced cases of Alzheimer's disease. In the peripheral nervous system, cholinergic neurons are implicated in the control of visceral functions such as, but not limited to, cardiac muscle contraction and gastrointestinal tract function.


Last edited by Cr6 on Thu May 31, 2018 12:11 am; edited 4 times in total

Cr6
Admin

Posts : 1033
Join date : 2014-08-09

View user profile http://milesmathis.forumotion.com

Back to top Go down

Re: Partial List of Superconductors to Build Out

Post by Cr6 on Thu May 31, 2018 12:04 am

Related on a completely different topic is the layout of this magnet? Do the Fe atoms link to the Nd atoms on each free alpha? If Hg and Ba are switched in for the Nds, then it becomes a S.C. -- just playing with these layouts. My apologies if this sounds too fast and loose.  

https://www.nevyns-lab.com/mathis/app/mbl/mbl.html?mbl=Nd-B-Nd-Fe14&align=X

Nd2Fe14B
Nd<sub>2</sub>Fe<sub>14</sub>B domain structure imaged with MOKE
Fig. 1 MOKE image of the fractal domain pattern of Nd2Fe14B taken in the group of our collaborator Prof. Ruslan Prozorov.

The rare-earth magnetic alloy Nd2Fe14B is one of the strongest known permanent magnets and is widely used in industrial and commercial applications. In the thermally demagnetized state, Nd2Fe14B magnets display a high degree of fine-scale (~25nm) magnetic texture [1-2] and branched fractal-like domains [3-4] along the c-axis, that make them of interest for magnetic microelectromechanical applications (`Mag-MEMS'). This material has been studied in the past using magnetic force microscopy (MFM) [1,2,4,5], scanning electron microscopy (SEM) [5], and magneto-optic Kerr effect (MOKE) microscopy [3,4,6]. Our magnetic force microscope has additional cababilities that enable us to study the magnetic domains at smaller length-scales and lower temepratures than previous studies. Furthermore, we employ harder magnetic tips which we hope to use for domain manipulation.

http://hoffman.physics.harvard.edu/materials/NdFeB.php


Last edited by Cr6 on Thu May 31, 2018 12:11 am; edited 1 time in total

Cr6
Admin

Posts : 1033
Join date : 2014-08-09

View user profile http://milesmathis.forumotion.com

Back to top Go down

Re: Partial List of Superconductors to Build Out

Post by Nevyn on Thu May 31, 2018 12:10 am

I don't know what makes it special. These are complex molecules in an even more complex environment. My guess would be the amount of charge flow they can support. When acetylcholine binds to a receptor, it injects or extracts charge from it and this allows other parts of that receptor to operate differently.

As an example, suppose it injects charge into the receptor. Then the receptor starts to expand, which opens up its walls and allows other molecules to slip through.

Just a guess and probably completely wrong. This is a long way from my comfort zone.
avatar
Nevyn
Admin

Posts : 1134
Join date : 2014-09-11

View user profile http://www.nevyns-lab.com

Back to top Go down

Re: Partial List of Superconductors to Build Out

Post by Nevyn on Thu May 31, 2018 12:16 am

That's a lot of iron!

I would guess that 8 of those go to the carousel levels of neodymium. That still leaves 6 to go in the main chain.

Maybe like this: (Fe-Fe-Nd[Fe,Fe,Fe,Fe])2-Fe-Fe-B
https://www.nevyns-lab.com/mathis/app/mbl/mbl.html?mbl=(Fe-Fe-Nd[Fe,Fe,Fe,Fe])2-Fe-Fe-B&align=X&atom=nucleus

avatar
Nevyn
Admin

Posts : 1134
Join date : 2014-09-11

View user profile http://www.nevyns-lab.com

Back to top Go down

Re: Partial List of Superconductors to Build Out

Post by Cr6 on Thu May 31, 2018 12:16 am

Nevyn wrote:

As an example, suppose it injects charge into the receptor. Then the receptor starts to expand, which opens up its walls and allows other molecules to slip through.

Just a guess and probably completely wrong. This is a long way from my comfort zone.

They do change their synaptic flow/ionic channelling by releasing chemical pre-cursors and such (charge related molecules) .  I'm thinking of how related cells may cause signaling for this as well. The brain's thought processes are pretty dependent on these reactions of glucose, glutamine and acetylcholine in just the right amounts.

And maybe why don't magnets/large metals near the head affect our thinking that much? These are just random thoughts on the topic. scratch (as I lift a 30lbs metal kettle bell above my head... lol... the jocks were always a little dumber in school and I blame the charge field!).

Cr6
Admin

Posts : 1033
Join date : 2014-08-09

View user profile http://milesmathis.forumotion.com

Back to top Go down

Re: Partial List of Superconductors to Build Out

Post by Cr6 on Thu May 31, 2018 12:31 am

I can see the "fractal-like domains" in the Fe and B. Cool as always. Is there room for fractals with Mathis at this level?


Fig. 1 MOKE image of the fractal domain pattern of Nd2Fe14B taken in the group of our collaborator Prof. Ruslan Prozorov.

http://hoffman.physics.harvard.edu/research/Hoffman-Laboratory-Research.pdf
http://hoffman.physics.harvard.edu/research.php

NbSe2


https://www.nevyns-lab.com/mathis/app/mbl/mbl.html?mbl=NbSe2&align=X

Cr6
Admin

Posts : 1033
Join date : 2014-08-09

View user profile http://milesmathis.forumotion.com

Back to top Go down

Re: Partial List of Superconductors to Build Out

Post by Nevyn on Thu May 31, 2018 12:49 am

Do you know how long it would have taken me to build that molecule in my (very) old desktop atomic viewer? Days! Days, I tell ya! Laughing
avatar
Nevyn
Admin

Posts : 1134
Join date : 2014-09-11

View user profile http://www.nevyns-lab.com

Back to top Go down

Re: Partial List of Superconductors to Build Out

Post by Nevyn on Thu May 31, 2018 12:55 am

If you wanted Nd2BFe14 a bit more symmetrical, then put the B in between the 2 middle Fe atoms instead of on the end. Not sure if that is required or not. If it was in the middle, it might cause a slight separation of charge flow between the 2 halves. Thus allowing southern charge to flow out of the carousel level of the southern Nd and the northern charge to flow out the carousel of the northern Nd. We want carousel output, as it is magnetic, so this might actually be the right choice.
avatar
Nevyn
Admin

Posts : 1134
Join date : 2014-09-11

View user profile http://www.nevyns-lab.com

Back to top Go down

Re: Partial List of Superconductors to Build Out

Post by Cr6 on Thu May 31, 2018 12:55 am

Nevyn wrote:Do you know how long it would have taken me to build that molecule in my (very) old desktop atomic viewer? Days! Days, I tell ya! Laughing
Lol! I hear you! And I was excited to just look at it back in the day!

http://www.fractaluniverse.org/v2/?page_id=131
https://www.eurekalert.org/pub_releases/2015-09/ciot-afi092115.php


Public Release: 21-Sep-2015
Atomic fractals in metallic glasses

California Institute of Technology

The group did simulations and experiments to probe the atomic structure of metallic glass alloys of copper, zirconium, and aluminum. In crystalline solids like diamond or gold, atoms or molecules are arranged in an orderly lattice pattern. As a result, the local neighborhood around an atom in a crystalline material is identical to everywhere else in the material. In amorphous metals, every location within the material looks different--except, Greer and her colleagues found, when you zoom in to look at the distribution of atoms at the scale of two to three atomic diameters--about one nanometer. At this level, the same fractal pattern is present, regardless of location within the material. "Within the clusters of atoms that make up a metallic glass, atoms are arranged in a particular kind of fractal pattern called percolation," Chen says.

Other scientists have previously hypothesized that the atoms in metallic glasses are distributed fractally. However, this creates an apparent paradox: When atoms are distributed fractally, there should be empty space between them. However, metallic glasses--just like regular metals--are fully dense, meaning that they lack significant pockets of empty space.

"Our group has solved this paradox by showing that atoms are only arranged fractally up to a certain scale," Greer says. "Larger than that scale, clusters of atoms are packed randomly and tightly, making a fully dense material, just like a regular metal. So we can have something that is both fractal and fully dense."

The discovery was made with metallic glasses, but the group's conclusions about fractally arranged atomic structures can be applied to essentially any rigid amorphous material, like the glass in a windowpane or a frozen piece of chewing gum. "Amorphous metals can exhibit unique properties, like unusual strength and elasticity," Chen says. "Now that we know the structure of these materials, we can start studying how their atomic-level arrangement affects their large-scale properties."

In addition to applications within materials science, studies of naturally occurring fractal distributions are of high interest within the fields of mathematics, physics, and computer science. Fractals have been studied for centuries by mathematicians and physicists. Showing how they emerge in a metallic alloy provides a physical foundation for something that has only been studied theoretically.

###

Other Caltech co-authors on the paper, titled "Fractal atomic-level percolation in metallic glasses," include Qi An, a theoretical and computational materials scientist, and Professor William Goddard, the Charles and Mary Ferkel Professor of Chemistry, Materials Science, and Applied Physics.

Caltech's Cu46Zr54




Cr6
Admin

Posts : 1033
Join date : 2014-08-09

View user profile http://milesmathis.forumotion.com

Back to top Go down

Re: Partial List of Superconductors to Build Out

Post by Nevyn on Thu May 31, 2018 1:20 am

Umm, Yeah, I'm not making that one!
avatar
Nevyn
Admin

Posts : 1134
Join date : 2014-09-11

View user profile http://www.nevyns-lab.com

Back to top Go down

Re: Partial List of Superconductors to Build Out

Post by Cr6 on Mon Jun 04, 2018 12:54 am

FYI... I just updated the first page with all the links to render the S.C. molecules in the MBL Viewer:

http://milesmathis.forumotion.com/t456-partial-list-of-superconductors-to-build-out#3542

Cr6
Admin

Posts : 1033
Join date : 2014-08-09

View user profile http://milesmathis.forumotion.com

Back to top Go down

Re: Partial List of Superconductors to Build Out

Post by Sponsored content


Sponsored content


Back to top Go down

Page 2 of 2 Previous  1, 2

Back to top


 
Permissions in this forum:
You cannot reply to topics in this forum