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For AC Man: New type of quantum material discovered!!!

TarponatorTarponator Under a BridgePosts: 17,098 AG
For your edification:

U.S. and European physicists searching for an explanation for high-temperature superconductivity were surprised when their theoretical model pointed to the existence of a never-before-seen material in a different realm of physics: topological quantum materials.

In a new study due this week in the Early Edition of the Proceedings of the National Academy of Sciences (PNAS), Rice University theoretical physicist Qimiao Si and colleagues at the Rice Center for Quantum Materials in Houston and the Vienna University of Technology in Austria make predictions that could help experimental physicists create what the authors have coined a "Weyl-Kondo semimetal," a quantum material with an assorted collection of properties seen in disparate materials like topological insulators, heavy fermion metals and high-temperature superconductors.

All these materials fall under the heading of "quantum materials," ceramics, layered composites and other materials whose electromagnetic behavior cannot be explained by classical physics. In the words of noted science writer Philip Ball, quantum materials are those in which "the quantum aspects assert themselves tenaciously, and the only way to fully understand how the material behaves is to keep the quantum in view."

These quirky behaviors arise only at very cold temperatures, where they cannot be masked by the overwhelming forces of thermal energy. The most celebrated quantum materials are the high-temperature superconductors discovered in the 1980s, so named for their ability to conduct electrical current without resistance at temperatures well above those of traditional superconductors. Another classic example is the heavy fermion materials discovered in the late 1970s. In these, electrons appear to be effectively hundreds of times more massive than normal and, equally unusual, the effective electron mass seems to vary strongly as temperature changes.

A generation of theoretical physicists dedicated their careers to explaining the workings of quantum materials. Si's work focuses on the collective behavior that emerges in electronic materials undergoing transformation from one quantum state to another. It is near such points of transformation, or "quantum critical points," that phenomena like high-temperature superconductivity occur.

In 2001, Si and colleagues offered a new theory that explained how electronic fluctuations between two entirely different quantum states give rise to such behaviors at quantum critical points. The theory has allowed Si and colleagues to make a host of predictions about the quantum behavior that will arise in particular types of material as the materials are cooled to the quantum critical point. In 2014, Si was tapped to lead the Rice Center for Quantum Materials (RCQM), a universitywide effort that draws upon the work in more than a dozen Rice groups across the schools of Natural Sciences and Engineering.

"We have been absolutely fascinated by strongly correlated materials," Si said of his own group. "Collective behavior such as quantum criticality and high-temperature superconductivity have always been the center of our attention.

"Over the past two years, several experimental groups have reported nontrivial topology in solid-state conducting materials, but it's an open question whether there are conducting states that have nontrivial topology and are, at the same time, strongly interacting. No such materials have been realized, but there's a lot of interest in looking for them."

Read more here: https://www.sciencedaily.com/releases/2017/12/171219111958.htm
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