High-pressure studies on electronic transport properties of Te-substituted Bi2Se3-xTex topological insulators

Studies on the electrical transport properties of the 3D topological insulators Bi2Se3 under iso-electronic substitution of Te at Se sites and the application of external pressure have been performed to understand the evolution of its ground-state properties and to explore possible electronic phase transitions in Bi2Se3-xTex(x = 0-3) systems. While the external pressure suppresses the metallic behaviour of Bi2Se3 arising from defect charge carriers leading ultimately to non-metal behaviour, the effect of pressure on Te-doped samples x = 1-2 seems to be more striking, and causes multiple electronic phase transitions such as an insulator-to-metal transition (MIT) followed by pressure-induced superconducting transition at higher pressures. All the critical parameters such as critical pressure for the occurrence of MIT (P-MIT), superconductivity (Psc) and maximum pressure induced superconducting transition temperature (T-c,T-max) for given compositions are seen to exhibit maxima at x = 1.6 which is the composition that exhibits the most insulating behaviour with least concentration of defect charge carriers among the samples of Bi2Se3-xTex (x = 0-3) series. The superconducting transition temperature (TO decreases with increasing pressure in x = 1-2 samples, while it remains nearly constant for Bi2Te3. Based on the analysis of the experimental data it is surmised that the pressure-induced superconductivity seen in these systems is of conventional (BCS) type. Copyright (C) EPLA, 2018