Emergence of non-centrosymmetric topological insulating phase in BiTeI under pressure

TL;DR

This study demonstrates that applying pressure to BiTeI induces a transition from a giant Rashba semiconductor to a topological insulator, revealing a pressure-tunable interplay between Rashba effects and topological phases.

Contribution

First-principles calculations show pressure-induced topological phase transition in BiTeI, highlighting the interplay between Rashba spin splitting and topological insulating states.

Findings

BiTeI becomes a topological insulator under pressure

Giant Rashba spin splitting is highly pressure-tunable

Distinct Dirac surface states appear on opposite sides

Abstract

The spin-orbit interaction affects the electronic structure of solids in various ways. Topological insulators are one example where the spin-orbit interaction leads the bulk bands to have a non-trivial topology, observable as gapless surface or edge states. Another example is the Rashba effect, which lifts the electron-spin degeneracy as a consequence of spin-orbit interaction under broken inversion symmetry. It is of particular importance to know how these two effects, i.e. the non-trivial topology of electronic states and Rashba spin splitting, interplay with each other. Here we show, through sophisticated first-principles calculations, that BiTeI, a giant bulk Rashba semiconductor, turns into a topological insulator under a reasonable pressure. This material is shown to exhibit several unique features such as, a highly pressure-tunable giant Rashba spin splitting, an unusual pressure-induced quantum phase transition, and more importantly the formation of strikingly different Dirac surface states at opposite sides of the material.