# Nonlinear anomalous Hall effect in few-layer WTe2

## Abstract

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 current2,3,4,5,6. 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.

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## Data availability

The data supporting the plots within this paper and other findings of this study are available from the corresponding authors upon request.

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## Acknowledgements

The research was supported by ARO Award W911NF-17-1-0605 for sample fabrication and transport measurements, and the US Department of Energy, Office of Basic Energy Sciences under award no. DESC0013883 for optical measurements. It was also partially supported by the Cornell Center for Materials Research with funding from the NSF MRSEC program (DMR-1719875) for the low-temperature studies. This work was performed in part at Cornell NanoScale Facility, an NNCI member supported by NSF Grant NNCI-1542081. We also thank the David and Lucille Packard Fellowship and a Sloan Fellowship (K.F.M.) for support and G. Stiehl for fruitful discussions on the crystal symmetry properties of multilayer Td-WTe2.

## Author information

K.K. and T.L. fabricated the devices. E.S., T.L. and K.K. developed the experimental set-up and performed the measurements. K.K., T.L. and K.F.M. analysed the data. J.S. and K.F.M. developed the model and wrote the paper. All the authors discussed the results and commented on the manuscript.

Correspondence to Jie Shan or Kin Fai Mak.

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### Competing interests

The authors declare no competing interests.

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## Supplementary information

### Supplementary Information

Supplementary Figures 1–7, Supplementary Tables 1,2, Supplementary Notes 1–5, Supplementary References 1–3

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