Orbital polarization and third-order anomalous Hall effect in WTe2

TL;DR

This paper investigates the microscopic origins of the third-order anomalous Hall effect in WTe2, revealing the role of orbital polarization and Berry connection polarizability through experimental and theoretical analysis.

Contribution

It uncovers the orbital polarization mechanism behind the third-order AHE in WTe2, combining angle-dependent measurements and spectroscopic detection to elucidate the microscopic process.

Findings

Third-order AHE correlates with electric field-induced orbital magnetic moments.

Polar reflective magnetic circular dichroism detects orbital polarization.

Scaling law analysis reveals intrinsic and skew scattering contributions.

Abstract

The anomalous Hall effect (AHE) has been extended into the nonlinear regime, where the Hall voltage shows higher-order response to the applied current. Nevertheless, the microscopic mechanism of the nonlinear AHE remains unclear. Here we report the orbital polarization and its induced third-order AHE in few-layer WTe2 flakes. Through angle-dependent electric measurements, it is found that the third-order AHE is quite consistent with the electric field induced polarization of orbital magnetic moment caused by the Berry connection polarizability tensor, which is further directly detected by polar reflective magnetic circular dichroism spectroscopy. The microscopic mechanisms of third-order AHE are analyzed through the scaling law, that is, the opposite orbital magnetic moments (up or down) deflect to opposite directions driven by electric field induced Berry curvature, forming the intrinsic contribution; driven by the Magnus effect of the self-rotating Bloch electrons, the opposite orbital magnetic moments are scattered towards opposite transverse directions, resulting in the skew scattering.