THE SAIF's WORLD

New superconductor theory may revolutionize electrical engineering

"Nanostripes" of alternating electrons and holes (spaces where electrons should be that appear as positive charges) appear in this scanning tunneling microscope image of a copper-oxide superconductor, just one of many odd patterns seen in years of observations of high-temperature superconductors. Credit: Davis Research Group.

High-temperature superconductors exhibit a frustratingly varied catalog of odd behavior, such as electrons that arrange themselves into stripes or refuse to arrange themselves symmetrically around atoms. Now two physicists propose that such behaviors – and superconductivity itself – can all be traced to a single starting point, and they explain why there are so many variations.

This theory might be a step toward new, higher-temperature superconductors that would revolutionize electrical engineering with more efficient motors and generators and lossless power transmission.

J.C. Séamus Davis, the James Gilbert White Distinguished Professor in the Physical Sciences at Cornell and director of the Center for Emergent Superconductivity at Brookhaven National Laboratory, and Dung-Hai Lee, professor of physics at the University of California-Berkeley and faculty scientist at Lawrence Berkeley National Laboratory, describe their theory in the Oct. 7 issue of the Proceedings of the National Academy of Sciences.

The oddities, known as intertwined ordered phases, seem to interfere with superconductivity. "We now have a simple way to understand how they are created and hopefully this understanding will help us to know how to get rid of them," said Lee.

Superconductivity, where current flows with zero resistance, was first discovered in metals cooled almost to absolute zero. Recently, complex crystals of copper, iron and some other metals combined with trace elements have been found to superconduct at temperatures up to around 150 Kelvins (degrees Celsius above absolute zero). For the last 10 years, Davis has examined these materials with scanning tunneling microscopes so well insulated from vibration that they can scan a surface in steps smaller than the width of an atom, while measuring the energies of electrons under their probes. He has discovered several of the intertwined phases of high-temperature superconductors, which appear in scans as unexpected arrangements of the electronic structure, and found them to vary widely from one material to another.

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