US, Chinese scientists\' discovery may help find new superconductors

A group of U.S. and Chinese scientists have made a new discovery on iron-based compounds, which may help find new superconductors that can be used in power generation, transportation and other fields, Rice University said Monday. The university, based in Houston, the U.S. state of Texas, made the announcement in a published statement Monday, saying that the effort to create practical superconductors has moved a step forward with the finding, which appeared online in a new Nature Communications paper. A team led by Rice physicist Qimiao Si found two distinctly different iron-based compounds share common mechanisms for moving electrons. Understanding that mechanism may help researchers find even better superconductors, Si said. The work by Si and his team showed how the interactions between electron spins in the iron-based compounds drive superconductivity. This interaction is the strongest when the electronic system is close to the Mott transition, which Si described as the point where electrons teeter on the edge of free movement or being stuck in place. "Ironically, this regime of electron correlation produces poor electrical conduction above the superconducting transition temperature, so the optimized superconductivity arises out of a bad metal," said Rong Yu, the co-author of the paper who was a postdoctoral fellow at Rice until this summer, when he became an associate professor at Renmin University in Beijing. Part of the success of the work is to explain how superconductivity peaks of the two doped iron compounds have comparable transition temperatures, as has been observed experimentally. "The chalcogenides, in many regards, are different from the pnictides but have a superconductive transition temperature just as high. That was a major surprise in the field," Si said. The pursuit of superconductivity -- the ability of electrons to travel through a material with no resistance and producing no heat -- has been a great challenge. But the rewards will be worth it, Si said, because superconductors will bring about revolutions not only in power generation and distribution, but also transportation, computing, and medical imaging, among others.