Xia Wei, Bai Bo, Chen Xuejiao, Yang Yichen, Zhang Yang, Yuan Jian, Li Qiang, Yang Kunya, Liu Xiangqi, Shi Yang, Ma Haiyang, Yang Huali, He Mingquan, Li Lei, Xi Chuanying, Pi Li, Lv Xiaodong, Wang Xia, Liu Xuerong, Li Shiyan, Zhou Xiaodong, Liu Jianpeng, Chen Yulin, Shen Jian, Shen Dawei, Zhong Zhicheng, Wang Wenbo, Guo Yanfeng
School of Physical Science and Technology, <a href="https://ror.org/030bhh786">ShanghaiTech University</a>, Shanghai 201210, China.
ShanghaiTech Laboratory for Topological Physics, <a href="https://ror.org/030bhh786">ShanghaiTech University</a>, Shanghai 201210, China.
Phys Rev Lett. 2024 Nov 22;133(21):216602. doi: 10.1103/PhysRevLett.133.216602.
Generally, the dissipationless Hall effect in solids requires time-reversal symmetry breaking (TRSB), where TRSB induced by external magnetic field results in the ordinary Hall effect, while TRSB caused by spontaneous magnetization gives rise to the anomalous Hall effect (AHE) which scales with the net magnetization. The AHE is therefore not expected in antiferromagnets with vanishing small magnetization. However, large AHE was recently observed in certain antiferromagnets with noncollinear spin structure and nonvanishing Berry curvature. Here, we report another origin of AHE in a layered antiferromagnet EuAl_{2}Si_{2}, namely, the domain wall (DW) skew scattering with Weyl points near the Fermi level, in experiments for the first time. Interestingly, the DWs form a unique periodic stripe structure with controllable periodicity by external magnetic field, which decreases nearly monotonically from 975 nm at 0 T to 232 nm at 4 T. Electrons incident on DW with topological bound states experience strong asymmetric scattering, leading to a giant AHE, with the DW Hall conductivity (DWHC) at 2 K and 1.2 T reaching a record value of ∼1.51×10^{4} Scm^{-1} among bulk systems and being 2 orders of magnitude larger than the intrinsic anomalous Hall conductivity. The observation not only sets a new paradigm for exploration of large anomalous Hall effect, but also provides potential applications in spintronic devices.
一般来说，固体中的无耗散霍尔效应需要时间反演对称性破缺（TRSB），其中由外部磁场引起的TRSB导致普通霍尔效应，而由自发磁化引起的TRSB则产生与净磁化强度成比例的反常霍尔效应（AHE）。因此，在磁化强度极小的反铁磁体中预计不会出现AHE。然而，最近在某些具有非共线自旋结构和非零贝里曲率的反铁磁体中观察到了大的AHE。在这里，我们首次在实验中报道了层状反铁磁体EuAl₂Si₂中AHE的另一个起源，即费米能级附近具有外尔点的畴壁（DW）斜散射。有趣的是，DW形成了一种独特的周期性条纹结构，其周期性可通过外部磁场控制，该周期性从0 T时的975 nm几乎单调下降到4 T时的232 nm。入射到具有拓扑束缚态的DW上的电子经历强烈的不对称散射，导致巨大的AHE，在2 K和1.2 T时的DW霍尔电导率（DWHC）在体系统中达到创纪录的值~1.51×10⁴ S cm⁻¹，比本征反常霍尔电导率大2个数量级。这一观测结果不仅为探索大反常霍尔效应树立了新的范例，也为自旋电子器件提供了潜在应用。
