Strongly enhanced Berry dipole at topological phase transitions in BiTeI

TL;DR

This paper investigates how a pressure-induced topological phase transition in BiTeI leads to a significant enhancement of the Berry curvature dipole, providing measurable signatures of the transition through transport and optoelectronic experiments.

Contribution

It reveals the giant enhancement of the Berry curvature dipole at topological phase transitions in BiTeI, linking it to observable nonlinear Hall effects and advancing understanding of topological materials.

Findings

Berry dipole peaks at topological transition points

Nonlinear Hall conductivity increases over two orders of magnitude

Berry dipole orientation reverses between phases

Abstract

Transitions between topologically distinct electronic states have been predicted in different classes of materials and observed in some. A major goal is the identification of measurable properties that directly expose the topological nature of such transitions. Here we focus on the giant-Rashba material bismuth tellurium iodine (BiTeI) which exhibits a pressure-driven phase transition between topological and trivial insulators in three-dimensions. We demonstrate that this transition, which proceeds through an intermediate Weyl semi-metallic state, is accompanied by a giant enhancement of the Berry curvature dipole which can be probed in transport and optoelectronic experiments. From first-principles calculations, we show that the Berrry-dipole --a vector along the polar axis of this material-- has opposite orientations in the trivial and topological insulating phases and peaks at the insulator-to-Weyl critical points, at which the nonlinear Hall conductivity can increase by over two orders of magnitude.