Superconductivity, Magnetoresistance, Magnetic Anomaly and Crystal Structure of New Phases of Topological Insulators Bi2Se3 and Sb2Te3

Abstract

We synthesized a new metastable phase of Bi2Se3 topological insulator by a rapid quenching after a high-pressure-high-temperature treatment at P≈7.7 GPa; 673<T<1400 K. The structure of metastable phase is monoclinic P21/m type. We observed the zero-field magnetic susceptibility cusp and linear positive magnetoresistance indicating the topological insulator state. The annealing at 673 K during 2 hours resulted in complete reversible transformation into the initial crystalline rhombohedral structure. Also we synthesized bulk polycrystalline samples of metastable at ambient conditions monoclinic (C2/m) phase of Sb2Te3 by rapid quenching after a high-pressure–high-temperature treatment at P=3.7–7.7 GPa; T=873 K and found superconductivity with Tc=2 K. A zero-field magnetic susceptibility cusp and linear positive magnetoresistance indicate a topological insulator state.