‘Exotic’ superconductor with metallic surface discovered

LONDON - A Princeton University-led research team has discovered a new material with a split personality - part superconductor, part metal.

The discovery may have implications for the development of next-generation electronics that could transform the way information is stored and processed.

The new material - a crystal called a topological superconductor has two electronic identities at once. At very low temperatures, the interior of the crystal behaves like a normal superconductor, able to conduct electricity with zero resistance. At the same time, the surface is metallic, able to carry a current, albeit with some resistance.

This is in direct contrast to most existing materials that are classified as electronic states of matter, including metals, insulators and conventional superconductors, which are consistent in how they do, or don’t, conduct electricity. For example, every single atom of every single copper wire is able to carry a current, which dissipates a bit as it travels. Similarly, all the molecules in normal superconductors conduct electricity without resistance when the material is placed at the appropriate temperature.

“The known states of electronic matter are insulators, metals, magnets, semiconductors and superconductors, and each of them has brought us new technology,” said M. Zahid Hasan, an associate professor of physics at Princeton who led the research team.

“Topological superconductors are superconducting everywhere but on the surface, where they are metallic; this leads to many possibilities for applications.”

“These highly unusual superconductors are the most ideal nurseries to create and manipulate Majorana fermions, which could be used to do quantum computing in a fault-resistant way ” said L. Andrew Wray, the first author of the paper, who received his doctoral degree from Princeton in 2010.

“And because the particles would exist on a superconductor, it could be possible to manipulate them in low power-consumption devices that are not only ‘green,’ but also immune to the overheating problems that befall current silicon-based electronics.”

To make a superconductor with topological behavior, or unusual surface properties, Princeton chemistry professor Robert Cava and his research group invented a new kind of crystal by inserting atoms of copper into the atomic lattice structure of a semiconductor made out of the compound bismuth selenide. This process, called intercalation doping, is a method used to change the number of electrons in a material and tweak its electrical properties.

The scientists discovered that, with the right amount of doping, they were able to turn the crystal into a superconductor at very low temperatures — below 4 degrees Kelvin, or around -452 degrees Fahrenheit. However, initial laboratory-based results suggested that the superconductor cannot retain topological properties indefinitely, though they do persist for months if the material is kept in a vacuum.

The findings have been published in the journal Nature Physics. (ANI)