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Pressure-induced Superconductivity in Bi2−xSbxTe3−ySey
T. He, X. Yang, T. Taguchi, T. Ueno, K. Kobayashi, J. Akimitsu, H. Yamaoka, H. Ishii, Y.-F. Liao, H. Ota, H. Goto, R. Eguchi, K. Terashima, T. Yokoya, H. O. Jeschke, X. Wu, and Y. Kubozono*
We systematically investigated the pressure dependence of electrical transport and the crystal structure of topological insulator, Bi2−xSbxTe3−ySey, which showed no superconductivity down to 2.0 K at ambient pressure. The Bi2−xSbxTe3−ySey crystal showed two structural phase transitions under pressure, from rhombohedral structure (space group No. 166, R3¯m, termed phase I) to monoclinic structure (space group No. 12, C2/m, termed phase II), and from phase II to another monoclinic structure (space group No. 12, C2/m, termed phase III). Superconductivity appeared when applying pressure; actually the superconductivity of all Bi2−xSbxTe3−ySey samples emerged in phase I. The superconducting transition temperature, Tc, increased against pressure in a pressure range of 0–15 GPa for all Bi2−xSbxTe3−ySey samples, and the maximum Tc was 5.45 K, recorded at 13.5 GPa in Bi2−xSbxTe3−ySey at x=0 and y=1.0. The magnetic field (H) dependence of the R–T plot for Bi2−xSbxTe3−ySey was measured to characterize the superconducting pairing mechanism of pressure-induced superconducting phase.