Nonlinear planar magnetotransport as a probe of the topology of surface states

TL;DR

This paper demonstrates that nonlinear planar magnetotransport measurements can reveal the quantum metric of Dirac surface states in topological insulators, providing a new method to diagnose bulk topology.

Contribution

It introduces a novel approach to probe the quantum metric via nonlinear magnetotransport in topological insulators, linking surface state geometry to measurable transport signatures.

Findings

Quantum metric influences nonlinear magnetotransport signatures.

Intrinsic part of longitudinal magnetoconductivity reveals quantum metric.

Method distinguishes single Dirac cones as a diagnostic of bulk topology.

Abstract

It has been recently established that transport measurements in the nonlinear regime can give direct access to the quantum metric (QM): the real part of the quantum geometric tensor characterizing the geometry of the electronic wavefunctions in a solid. In topological materials, the QM has been so far revealed in thin films of the topological antiferromagnet MnBi$_2$Te$_4$ where it provides a direct contribution to longitudinal currents quadratic in the driving electric field. Here we show that the Dirac surface states of strong three-dimensional topological insulators have a QM that can be accessed from the nonlinear transport characteristics in the presence of an externally applied planar magnetic field. A previously unknown intrinsic part of the longitudinal magnetoconductivity carries the signature of the QM while coexisting with the extrinsic part responsible for the so-called bilinear magnetoelectric resistance. We prove that the QM-induced nonlinear magnetotransport carries specific signatures of single Dirac cones. This allows to use it as an efficient diagnostic tool of the bulk topology of three-dimensional non-magnetic insulators.