Low temperature amorphization and superconductivity in FeSe single crystals at high pressures


In this study, we report low temperature x-ray diffraction studies combined with electrical resistance measurements on single crystals of iron-based layered superconductor FeSe to a temperature of 10 K and a pressure of 44 GPa. The low temperature high pressure x-ray diffraction studies were performed using a synchrotron source and superconductivity at high pressure was studied using designer diamond anvils. At ambient temperature, the FeSe sample shows a phase transformation from a PbO-type tetragonal phase to a NiAs-type hexagonal phase at 10 +/- 2 GPa. On cooling, a structural distortion from a PbO-type tetragonal phase to an orthorhombic Cmma phase is observed below 100 K. At a low temperature of 10 K, compression of the orthorhombic Cmma phase results in a gradual transformation to an amorphous phase above 15 GPa. The transformation to the amorphous phase is completed by 40 GPa at 10 K. A loss of superconductivity is observed in the amorphous phase and a dramatic change in the temperature behavior of electrical resistance indicates formation of a semiconducting state at high pressures and low temperatures. The formation of the amorphous phase is attributed to a kinetic hindrance to the growth of a hexagonal NiAs phase under high pressures and low temperatures.





Stemshorn,Andrew K.;Tsoi,Georgiy;Vohra,Yogesh K.;Sinogeiken,Stanislav;Wu,Phillip M.;Huang,Yilin;Rao,Sistla M.;Wu,Maw-Kuen;Yeh,Kuo W.;Weir,Samuel T.. 2010. Low temperature amorphization and superconductivity in FeSe single crystals at high pressures. Journal of Materials Research 25(2): 396-400.

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