Local insight to the structural phase transition sequence of Bi2Se3 under quasi-hydrostatic and nonhydrostatic pressure

Abstract

Abstract High-pressure behaviors of Bi2Se3, as one of layered 3D topological insulators, has attracted tremendous interest recent years. However, the phase transition sequence of Bi2Se3 remain controversial. In this work, we explore the structural phase sequence of topological insulator Bi2Se3 using high-pressure x-ray absorption fine structure (XAFS) spectroscopy under quasi-hydrostatic and nonhydrostatic pressure up to 42 GPa. By examining the XAFS features, we find that the appearance of C2/c phase of Bi2Se3 is strongly dependent on pressure condition, C2/c phase of Bi2Se3 only exists under quasi-hydrostatic pressure condition. The phonon dispersion calculations also show that C2/c phase is dynamic unstable. Furthermore, we confirm that Bi2Se3 possesses I4/mmm phase rather than Im-3m and 9/10-fold C2/m phase at high pressure. Combining the experimental and theoretical results, we determine the structural phase transition sequence for Bi2Se3 of R-3m → C2/m → C2/c → I4/mmm phase under quasi-hydrostatic pressure condition and R-3m → C2/m → I4/mmm phase under nonhydrostatic pressure condition. The dynamic unstability and pressure condition sensitivity of C2/c phase may be account for the absence of C2/c phase in the phase transition sequence under nonhydrostatic pressure condition. Our findings obtain the high-pressure phase transition sequences of Bi2Se3 under hydrostatic and nonhydrostatic pressure condition, which can facilitate researchers to explore the novel properties in layered 3D topological insulators.