Physics

Electron

Spin Hall effect

Geometric phase

Dipole

Point reflection

Magnetization

Magnetic field

Hall effect

Spin polarization

Berry connection and curvature

Condensed matter physics

Quantum mechanics

Thermal Hall effect

Nature Materials

The Hall effect occurs only in systems with broken time-reversal symmetry, such as materials under an external magnetic field in the ordinary Hall effect and magnetic materials in the anomalous Hall effect (AHE)1. Here we show a nonlinear AHE in a non-magnetic material under zero magnetic field, in which the Hall voltage depends quadratically on the longitudinal current2–6. We observe the effect in few-layer Td-WTe2, a two-dimensional semimetal with broken inversion symmetry and only one mirror line in the crystal plane. Our angle-resolved electrical measurements reveal that the Hall voltage 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 the intrinsic Berry curvature dipole and extrinsic spin-dependent scatterings contribute to the observed nonlinear AHE. A nonlinear anomalous Hall effect, allowed for certain point group symmetries, is observed in metallic WTe2.

Nonlinear anomalous Hall effect in few-layer WTe2