Self-doping may be the key to superconductivity in room temperature

Swedish materials researchers at Linköping and Uppsala University and Chalmers University of Technology, in collaboration with researchers at the Swiss Synchrotron Light Source (SLS) in Switzerland investigated the superconductor YBa2Cu3O7-x (abbreviated YBCO) using advanced X-ray spectroscopy.

Their findings are published in the Nature journal Science Reports.

YBCO is a well-known ceramic copper-based material that can conduct electricity without loss (superconductivity) when it is cooled below its critical temperature Tc=-183° C. Since the resistance and energy losses are zero in superconductors, there exist many technologically interesting and energy-saving electrical applications as well as benefits to the transport industry. Electromagnets in electric motors can be made smaller with stronger magnetic fields that are more powerful yet consume less energy; magnetic levitating trains that exploit superconductor technology can reach higher speeds by avoiding friction against rails.

On the other hand, the necessity of cooling these materials to low temperatures remains to be an obstacle one would like to eliminate. Therefore, one of the major objectives of superconductor research is trying to find a material that is superconducting at room temperature. However, the mechanism that underlies high-temperature superconductivity is still not entirely understood. In this work, the researchers have made a discovery that may shed new light on this phenomenon. X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS) was used for measuring YBCO at room temperature and at -258° C, which is far below Tc.