First investigation of pressure effects on transition from superconductive to metallic phase in FeSe _0.5Te _0.5

High-pressure resistivity experiments were performed on FeSe _0.5Te _0.5. The onset temperature of T _c (T ^onset _c) increases rapidly from 13.5 to 26.2K upon applying pressure up to 2 GPa. Above 2 GPa, T _c decreases linearly and the metallic phase was observed at P 14 GPa. The same relationship between normalized T _c and pressure in both FeSe _0.5Te _0.5 and FeSe suggests a universal pressure dependence in this system. This report presents the first observation of a phase transition from the superconducting to the metallic phase on the P-T _c phase diagram.