Superconductivity at 27 K in tetragonal FeSe under high pressure

A huge enhancement of the superconducting transition temperature T(c) was observed in a tetragonal FeSe superconductor under high pressure. The onset temperature was as high as 27 K at 1.48 GPa and the pressure coefficient showed an extremely high value of 9.1 K/GPa. The upper critical field H(c2) was estimated to be similar to 72 T at 1.48 GPa. Because of the high H(c2), the FeSe system can be applied to superconducting wire rods. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.3000616]