Pressure-induced phase transition in Bi$_2$Se$_3$ at 3 GPa: electronic topological transition or not?

TL;DR

This study investigates the pressure-induced phase transition in Bi$_2$Se$_3$ around 3 GPa, combining Raman spectroscopy and first-principles calculations, and finds no evidence of an electronic topological transition at this pressure.

Contribution

It provides experimental and theoretical evidence that the phase transition near 3 GPa in Bi$_2$Se$_3$ is not an electronic topological transition, clarifying previous ambiguities.

Findings

Raman signatures indicate an isostructural transition at ~2.4 GPa.

Structural transitions occur at ~10 GPa and 16 GPa.

No change in electronic topology at 3 GPa as per calculations.

Abstract

In recent years, a low pressure transition around P $\sim$ 3 GPa exhibited by the A$_2$B$_3$-type 3D topological insulators is attributed to an electronic topological transition (ETT) for which there is no direct evidence either from theory or experiments. We address this phase transition and other transitions at higher pressure in bismuth selenide (Bi$_2$Se$_3$) using Raman spectroscopy at pressure upto 26.2 GPa. We see clear Raman signatures of an isostructural phase transition at P $\sim$ 2.4 GPa followed by structural transitions at $\sim$ 10 GPa and 16 GPa. First-principles calculations reveal anomalously sharp changes in the structural parameters like the internal angle of the rhombohedral unit cell with a minimum in the c/a ratio near P $\sim$ 3 GPa. While our calculations reveal the associated anomalies in vibrational frequencies and electronic bandgap, the calculated $\mathbb{Z}_2$ invariant and Dirac conical surface electronic structure remain unchanged, showing that there is no change in the electronic topology at the lowest pressure transition.