Universal superconductivity phase diagram for pressurized tetradymite topological insulators

Abstract

© 2018 American Physical Society. We show that two different superconducting phases exist at high pressures in the optimized tetradymite topological insulators Bi2Te2Se (BTS) and Bi1.1Sb0.9Te2S (BSTS). The superconducting phases emerge at structural phase transitions; the first at ∼8.4GPa for BTS and ∼12.4GPa for BSTS, and the second at 13.6 GPa for BTS and 20.4 GPa, for BSTS. Electronic structure calculations show that these phases do not have topological character. Comparison of our results with prior work on Bi2Se3, Bi2Te3, and (Bi,Sb)2(Se,Te)3 allows us to uncover a universal phase diagram for pressure-induced superconductivity in tetradymites, providing a basis for understanding the relationships between topological behavior, crystal structure, and superconductivity for these materials.