Observation of the nonlinear anomalous Hall effect in 2D WTe2

TL;DR

This paper reports the discovery of a nonlinear anomalous Hall effect in nonmagnetic 2D WTe2, driven by current-induced magnetization and Berry curvature, revealing new physics in nonlinear electrical transport.

Contribution

It demonstrates the existence of a nonlinear AHE in nonmagnetic WTe2, driven by current-induced magnetization and Berry curvature effects, a novel phenomenon in 2D materials.

Findings

Nonlinear AHE observed in 2D WTe2 at zero magnetic field.

Hall voltage depends quadratically on the current and reverses with current direction.

Both intrinsic Berry curvature and extrinsic scattering contribute to the effect.

Abstract

The Hall effect occurs only in systems with broken time-reversal symmetry, such as solids under an external magnetic field in the ordinary Hall effect and magnetic materials in the anomalous Hall effect (AHE). Here we show a new Hall effect in a nonmagnetic material under zero magnetic field, in which the Hall voltage depends quadratically on the longitudinal current. We observe the effect (referred to as nonlinear AHE) in two-dimensional Td-WTe2, a semimetal with broken inversion symmetry and only one mirror line in the crystal plane. Our angle-resolved electrical measurements reveal that the Hall voltage changes sign when the bias current reverses direction; it maximizes (vanishes) when the bias current is perpendicular (parallel) to the mirror line. The observed effect can be understood as an AHE induced by the bias current which generates an out-of-plane magnetization. The temperature dependence of the Hall conductivity further suggests that both intrinsic Berry curvature dipole and extrinsic spin-dependent scatterings contribute to the observed nonlinear AHE. Our results open the possibility of exploring the intrinsic Berry curvature effect in nonlinear electrical transport in solids .