Superconductivity, Einstein team up

UC SANTA BARBARA (US) — Scientists have used Einstein’s theory of relativity to demonstrate it is possible to reproduce the Josephson junction, a main ingredient in superconductivity applications.

Einstein’s theory—which was developed as a theory of gravity and is extremely successful in explaining a wide variety of gravitational phenomena—is now being used to explain several aspects of non-gravitational physics.

“The basic phenomenon with Josephson junctions is that you can take two superconductors, separate them by a little gap, and still find current going across it, in a specific way,” says Gary Horowitz, professor of physics at the University of California, Santa Barbara.

“And that has found many applications. So the Josephson junction is something we’ve reproduced using general relativity.”

The research is published in the journal Physical Review Letters.

Researchers used tools from string theory to develop the gravity model of a superconductor. Horowitz says they were surprised to be able to link Einstein’s general theory of relativity to a totally different area of physics and hope the tools will one day be able to shed light on new types of superconductors.

“Most materials, if you cool them down sufficiently, will actually conduct electricity without any resistance,” he says. “These are superconductors. There is a standard theory of superconductivity, discovered about 50 years ago, that has worked well for most of the so-called conventional superconductors.”

Physicists are still working on understanding a new class of materials—superconductors that have zero resistance at somewhat higher temperatures were discovered 25 years ago.

The materials involves copper-oxygen planes. Another new class of superconductors, based on iron instead of copper, was discovered a couple of years ago. These materials, called iron nictides, also have the property of superconducting at a higher temperature.

“There is a lot of activity and interest in understanding these materials,” Horowitz says. “Ultimately, the goal is to have a room-temperature superconductor, which, you can imagine, would have lots of interesting applications.”

Horowitz and colleagues found what could be called a gravitational model,
or a gravitational dual––a dual description of a superconductor using gravity, black holes, and all of the traditional ingredients of general relativity.

“This came as quite a surprise because this is a totally different area of physics, which is now being connected to this condensed matter area”

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