Strongly enhanced Berry-dipole at topological phase transitions in BiTeI

FACIO, JORGE I.; EFREMOV, DMITRI; KOEPERNIK, KLAUS; YOU, JHIH-SHIH; SODEMANN, INTI; VAN DEN BRINK, JEROEN

Dresden

Conferencia; International SFB conference "Frustration and Topology?; 2018

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.