Rashba asymmetric topological insulator BiTeCl under compression: equation of state, vibrational features and electronic properties

Abstract

We present an in-depth characterization of the structural, vibrational, and electronic properties of the Rashba asymmetric topological insulator BiTeCl under high-pressure conditions (10 GPa) from an experimental and theoretical perspective. X-ray diffraction and Raman spectroscopy measurements reveal an incomplete and reversible phase transition to an allegedly less symmetric structure at a pressure above 5 GPa. The experimental equation of state and the axial compressibility of BiTeCl are reported and discussed, as well as a detailed analysis of the evolution of its vibrational features. The electronic band structure of BiTeCl is calculated and its behavior under compression is discussed, with emphasis on the behavior of the band gap and the increase of the Rashba splitting, which is found to be weakly anisotropic. An analysis of the electron density topology indicates that the low-pressure phase of BiTeCl is characterized by intralayer electron-deficient multicenter Bi–Te and Bi–Cl bonds and that interlayer bonds are not purely van der Waals in nature.