Low temperature amorphization and superconductivity in FeSe single crystals at high pressures
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Low temperature amorphization and superconductivity in FeSe single crystals at high pressures Andrew K. Stemshorn, Georgiy Tsoi, and Yogesh K. Vohraa) Department of Physics, University of Alabama at Birmingham, Birmingham, Alabama 35294
Stanislav Sinogeiken High Pressure Collaborative Access Team (HPCAT), Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439
Phillip M. Wu Department of Physics, Duke University, Durham, North Carolina 27708
Yilin Huang, Sistla M. Rao, Maw-Kuen Wu, and Kuo W. Yeh Institute of Physics, Academia Sinica, Nankang, Taipei 115, Taiwan
Samuel T. Weir L-041, Lawrence Livermore National Laboratory, Livermore, California 94550 (Received 28 June 2009; accepted 9 September 2009)
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 NiAstype 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.
The superconductivity in the PbO-type structure bFeSe was discovered recently at 8 K in samples prepared with Se deficiency.1 The occurrence of superconductivity in this simple layered FeSe compound with edge-sharing FeSe4 tetrahedron has created tremendous interest in the effects of chemical substitution and high pressure on this material system.2 In particular, tellurium (Te) substitution has been studied3,4 and a maximum superconducting transition temperature of 15.2 K was measured for FeSe0.5Te0.5. Additionally, pressure-induced enhancement of the superconducting transition temperature of
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Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2010.0044
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http://journals.cambridge.org
J. Mater. Res., Vol. 25, No. 2, Feb 2010 Downloaded: 14 Mar 2015
the FeSeTe system has been reported4,5 that warrants further high-pressure structural investigations at low temperatures. A recent high-pressure study6 on the FeSe0.5 Te0.5 compound reported a pressure-induced tetragonal to amorphous phase transfor
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