High-pressure topological transport study of Bi2Se3 single crystal

Abstract

Herein we report the topological transport on compressed Bi2Se3 single crystal, one of ideally topological insulators, based on a combination of in-situ alternating current (AC) impedance spectra and direct current (DC) conductivity methods at room temperature. The insulating bulk and metallic surface states of the sample are well divided into two relaxation processes according to their different responses on electric excitation. We find that the surface state conductivity remains constant in the face of one order of magnitude increase in the bulk state conductivity. The first-principles calculations are adopted to account for the bulk transport results. The band structures calculations reveal the gradual decrease in the intrinsic bandgap with pressure elevation. The variations of charge density difference demonstrate the strengthened interatomic interactions and the formation of small polarons due to the electrons overlap assisted by the lattice shrinking under high pressure. By the pressure dependences of electrical parameters and the relationship between them, a reasonable electrical model of topological insulators is well established and opens up a new way for the exploration of topological architectures under extreme conditions.