Transport and structural properties of Cu0.25Bi2(Te x Se1− x )3 (x = 0.01) under high pressure

Cu0.25Bi2(TexSe1-x)(3) is a material in which tellurium atoms (Te) partially occupy selenium (Se) sites in a crystal structure of the superconductor Cu0.25Bi2Se3. This study focuses on the composition of x = 0.01, Cu0.25Bi2(Te0.01Se0.99)(3), and we performed electrical resistivity measurement and X-ray diffraction under high pressures. Cu0.25Bi2(Te0.01Se0.99)(3) shows slight diamagnetism and a drop in resistivity at ambient pressure; this suggests possible superconductivity at the transition temperature of T-c = 3.2K, which is suppressed at P = 1 GPa. On further compression, a slight drop in resistivity is observed at temperatures of 4.3-5.4K above 10 GPa. This drop is suppressed under magnetic fields, suggesting the occurrence of superconducting transition. The pressure-induced structural phase transition from a trigonal R3m phase to a sevenfold monoclinic C2/m phase occurs at 10.9 GPa. These results suggest that the superconducting transition above 10 GPa occurs in the high-pressure C2/m phase. (c) 2017 The Japan Society of Applied Physics