Scientists find a solution to long-standing mysteries of cuprate high-temperature superconductivity

Scientists who have tried to gain a better understanding of the intricacies of high-temperature superconductivity, which is the ability of certain materials to carry electrical current without energy loss, have been confused by the mysterious phase that happens when charge carriers are added which appear to compete with superconductivity.


It has also been a mystery why, the movement of superconducting electrons appears to be restricted to certain directions within this “pseudogap”. The pivotal challenge has been exploring this pseudogap and whether, and also how it affects the movement of electrons.


A team of scientists at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory and Cornell University has now used unique capabilities to reveal detailed characteristics of the electrons in one of these materials as it transforms from an insulator through the mysterious pseudogap phase and eventually into a full-blown superconductor.


Two distinct personality changes in the material’s electrons was described in the May 9, 2014 issue of Science. They include, the disappearance of a rather exotic periodic static arrangement of certain electrons within the pseudogap phase and the sudden ability of all the material’s electrons to move freely in any direction.


This finding strengthens support for the idea that the periodic arrangement, sometimes referred to as “stripes” or “density waves”, restricts the flow of electrons and impairs maximal superconductivity in the pseudogap phase.


“This is the first time an experiment has directly linked the disappearance of the density waves and their associated nanoscale crystal distortions with the emergence of universally free-flowing electrons needed for unrestricted superconductivity,” said lead author J.C. Séamus Davis, a senior physicist and Director of DOE’s Center of Emergent Superconductivity at Brookhaven Lab and also a professor at both Cornell University and the St. Andrews University in Scotland. “These new measurements finally show us why, in the mysterious pseudogap state of this material, the electrons are less free to move.”

Armed with this information, scientists may be able to come up with ways to get superconductivity flowing under more favorable conditions. However, for now, even these “high-temperature” copper-oxide materials operate as superconductors only when they are cooled below -100 degrees Celsius. “That’s room temperature during a particularly bad winter in Antarctica,” Davis said. Scientists are hoping to find ways to raise the operating temperature for real-world energy-saving applications, like highly efficient power generation and transmission and computers that work at speeds thousands of times faster than the ones available today.

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