### 摘要

The electrical Hall effect is the production, upon the application of an electric field, of a transverse voltage under an out-of-plane magnetic field. Studies of the Hall effect have led to important breakthroughs, including the discoveries of Berry curvature and topological Chern invariants ^{1,2} . The internal magnetization of magnets means that the electrical Hall effect can occur in the absence of an external magnetic field ^{2} ; this ‘anomalous’ Hall effect is important for the study of quantum magnets ^{2–7} . The electrical Hall effect has rarely been studied in non-magnetic materials without external magnetic fields, owing to the constraint of time-reversal symmetry. However, only in the linear response regime—when the Hall voltage is linearly proportional to the external electric field—does the Hall effect identically vanish as a result of time-reversal symmetry; the Hall effect in the nonlinear response regime is not subject to such symmetry constraints ^{8–10} . Here we report observations of the nonlinear Hall effect ^{10} in electrical transport in bilayers of the non-magnetic quantum material WTe _{2} under time-reversal-symmetric conditions. We show that an electric current in bilayer WTe _{2} leads to a nonlinear Hall voltage in the absence of a magnetic field. The properties of this nonlinear Hall effect are distinct from those of the anomalous Hall effect in metals: the nonlinear Hall effect results in a quadratic, rather than linear, current–voltage characteristic and, in contrast to the anomalous Hall effect, the nonlinear Hall effect results in a much larger transverse than longitudinal voltage response, leading to a nonlinear Hall angle (the angle between the total voltage response and the applied electric field) of nearly 90 degrees. We further show that the nonlinear Hall effect provides a direct measure of the dipole moment ^{10} of the Berry curvature, which arises from layer-polarized Dirac fermions in bilayer WTe _{2} . Our results demonstrate a new type of Hall effect and provide a way of detecting Berry curvature in non-magnetic quantum materials.

原文 | English |
---|---|

頁（從 - 到） | 337-342 |

頁數 | 6 |

期刊 | Nature |

卷 | 565 |

發行號 | 7739 |

DOIs | |

出版狀態 | Published - 2019 一月 17 |

### 指紋

### All Science Journal Classification (ASJC) codes

- General

### 引用此

*Nature*,

*565*(7739), 337-342. https://doi.org/10.1038/s41586-018-0807-6