Arun Bansil and Robert Markiewicz on Superconductivity in cuprates - Superconductor or not? Exploring the identity crisis of this weird quantum material

(Much more at link:  https://phys.org/news/2020-01-superconductor-exploring-identity-crisis-weird.html)

JANUARY 3, 2020

Superconductor or not? Exploring the identity crisis of this weird quantum material
by Roberto Molar Candanosa, Northeastern University

Arun Bansil, University Distinguished Professor of physics and Robert Markiewicz, professor of physics, are part of a team of researchers who are describing the mechanism by which copper-oxide materials turn from insulators to superconductors. Credit: Matthew Modoono/Northeastern University

Northeastern researchers have used a powerful computer model to probe a puzzling class of copper-based materials that can be turned into superconductors. Their findings offer tantalizing clues for a decades-old mystery, and a step forward for quantum computing.

The ability of a material to let electricity flow comes from the way electrons within their atoms are arranged. Depending on these arrangements, or configurations, all materials out there are either insulators or conductors of electricity.

But cuprates, a class of mysterious materials that are made from copper oxides, are famous in the scientific community for having somewhat of an identity issue that can make them both insulators and conductors.

Under normal conditions, cuprates are insulators: materials that inhibit the flow of electrons. But with tweaks to their composition, they can transform into the world's best superconductors.

The finding of this kind of superconductivity in 1986 won its discoverers a Nobel Prize in 1987, and fascinated the scientific community with a world of possibilities for improvements to supercomputing and other crucial technologies.

But with fascination came 30 years of bewilderment: Scientists have not been able to fully decipher the arrangement of electrons that encodes for superconductivity in cuprates. (Miles Mathis has shown this hasn't he? --Cr6)

Mapping the electronic configuration of these materials is arguably one of the toughest challenges in theoretical physics, says Arun Bansil, University Distinguished Professor of physics at Northeastern. And, he says, because superconductivity is a weird phenomenon that only happens at temperatures as low as -300 F (or about as cold as it gets on Uranus), figuring out the mechanisms that make it possible in the first place could help researchers make superconductors that work at room temperature.

Now, a team of researchers that includes Bansil and Robert Markiewicz, a professor of physics at Northeastern, is presenting a new way to model these strange mechanisms that lead to superconductivity in cuprates.

Bansil likes to think of this complexity as butterflies inside a jar flying fast and cleverly to avoid colliding with each other. In a conducting material, electrons also move around. And because of a combination of physical forces, they also avoid each other. Those characteristics are at the core of what makes it hard to model cuprate materials.