Kang Kaifei, Li Tingxin, Sohn Egon, Shan Jie, Mak Kin Fai
School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA.
Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, NY, USA.
Nat Mater. 2019 Apr;18(4):324-328. doi: 10.1038/s41563-019-0294-7. Epub 2019 Feb 25.
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). 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 current. We observe the effect in few-layer T-WTe, 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.
霍尔效应仅发生在时间反演对称性破缺的系统中，例如在普通霍尔效应中处于外部磁场下的材料以及反常霍尔效应（AHE）中的磁性材料。在此，我们展示了在零磁场下非磁性材料中的非线性反常霍尔效应，其中霍尔电压与纵向电流呈二次方关系。我们在少层T-WTe中观察到了这种效应，T-WTe是一种二维半金属，具有反演对称性破缺且在晶面中仅有一条镜面线。我们的角分辨电学测量表明，当偏置电流垂直（平行）于镜面线时，霍尔电压达到最大值（消失）。观察到的效应可理解为由偏置电流诱导的反常霍尔效应，该电流会产生面外磁化。霍尔电导率的温度依赖性进一步表明，本征贝里曲率偶极子和外在自旋相关散射都对观察到的非线性反常霍尔效应有贡献。
