Observation of the nonlinear anomalous Hall effect in 2D WTe2

Understand

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.