Abstract

A topological phase transition from a trivial insulator to a $\mathbb{Z}_2$ topological insulator requires the bulk band gap to vanish. In the case of noncentrosymmetric materials, these phases are separated by a gapless Weyl semimetal phase. However, at finite temperature, the gap is affected by atomic motion, through electron-phonon interaction, and by thermal expansion of the lattice. As a consequence, the phase space of topologically nontrivial phases is affected by temperature. In this paper, the pressure and temperature dependence of the indirect band gap of BiTeI is investigated from first principles. We evaluate the contribution from both electron-phonon interaction and thermal expansion, and show that their combined effect drives the topological phase transition towards higher pressures with increasing temperature. Notably, we find that the sensitivity of both band extrema to pressure and topology for electron-phonon interaction differs significantly according to their leading orbital character. Our results indicate that the Weyl semimetal phase width is increased by temperature, having almost doubled by 100 K when compared to the static lattice results. Our findings thus provide a guideline for experimental detection of the nontrivial phases of BiTeI and illustrate how the phase space of the Weyl semimetal phase in noncentrosymmetric materials can be significantly affected by temperature.

Highlights

  • Topological phases of matter have become a thriving field of condensed matter physics, for both fundamental and applied research [1]

  • BiTeI is a layered material composed of alternating Bi, Te, and I planes stacked along the high-symmetry crystallographic caxis

  • We have characterized the temperature dependence of the topological phase transition in BiTeI using first-principles methodologies based on density-functional perturbation theory (DFPT)

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Summary

Introduction

Topological phases of matter have become a thriving field of condensed matter physics, for both fundamental and applied research [1]. The discovery of experimentally tunable topological phases, whether through stoichiometric doping [3,4,5,6], hydrostatic pressure [7,8], strain [9,10], external electric fields [11,12], or interaction with light [13,14], has led to a continually growing number of proposals for promising and innovative applications relying on the refined engineering of these robust states and their associated phase transitions [15,16,17,18] Another widely studied class of materials is the bulk Rashba semiconductors, in which a strong spin-orbit interaction combined with the absence of inversion symmetry leads to a splitting of electronic bands of opposite spin polarization [19,20].

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