Simultaneous measurement of pressure evolution of crystal structure and superconductivity in FeSe0.92 using designer diamonds

Simultaneous high-pressure X-ray diffraction and electrical resistance measurements have been carried out on a PbO-type alpha-FeSe0.92 compound to a pressure of 44 GPa and temperatures down to 4 K using designer diamond anvils at synchrotron source. At ambient temperature, a structural phase transition from a tetragonal (P4/nmm) phase to an orthorhombic (Pbnm) phase is observed at 11 GPa and the Pbnm phase persists up to 74 GPa. The superconducting transition temperature (T-C) increases rapidly with pressure reaching a maximum of similar to 28 K at similar to 6 GPa and decreases at higher pressures, disappearing completely at 14.6 GPa. Simultaneous pressure-dependent X-ray diffraction and resistance measurements at low temperatures show superconductivity only in a low-pressure orthorhombic (Cmma) phase of the alpha-FeSe0.92. Upon increasing pressure at 10 K near T-C, crystalline phases change from a mixture of orthorhombic (Cmma) and hexagonal (P63/mmc) phases to a high-pressure orthorhombic (Pbnm) phase near 6.4 GPa where T-C is maximum. Copyright (C) EPLA, 2012