Layer Hall effect in a 2D topological axion antiferromagnet
Layer Hall effect in a 2D topological axion antiferromagnet
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DOI：
10.1038/s41586-021-03679-w
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发表时间：
2021-07-22
期刊：
影响因子：
64.8
通讯作者：
Xu, Su-Yang
中科院分区：
文献类型：
--
作者：
Gao, Anyuan;Liu, Yu-Fei;Xu, Su-Yang
虽然铁磁体已经被发现和使用了几千年，但反铁磁体直到20世纪30年代才被发现。在大尺度上，由于没有整体磁化，反铁磁体似乎表现得像任何非磁性材料。然而，在微观水平上，自旋的相反排列形成了丰富的内部结构。在拓扑反铁磁体中，这种内部结构导致了被称为Berry相的性质可以获得不同的空间纹理的可能性（2，3）。在这里，我们研究这种可能性在反铁磁轴子绝缘体，甚至分层，二维MnBi 2 Te 4-在其中的空间自由度对应于不同的层。我们观察到一种类型的霍尔效应-层霍尔效应-其中来自顶层和底层的电子自发地向相反的方向偏转。具体地，在零电场下，均匀层状MnBi_2Te_4没有显示出异常霍尔效应。然而，施加电场会导致出现一个大的，层极化的异常霍尔效应，约为0.5e（2）/h（其中e是电子电荷，h是普朗克常数）。这层霍尔效应揭示了一个不寻常的层锁贝里曲率，这是用来表征轴子绝缘体状态。此外，我们发现层锁Berry曲率可以通过由电场和磁场矢量的点积形成的轴子场来操纵。我们的研究结果提供了新的途径来检测和操纵完全补偿拓扑反铁磁体的内部空间结构（4-9）。层锁定的Berry曲率代表了通过诸如层特定的莫尔电位的效应实现Berry相位的空间工程的第一步。
Whereas ferromagnets have been known and used for millennia, antiferromagnets were only discovered in the 1930s(1). At large scale, because of the absence of global magnetization, antiferromagnets may seem to behave like any non-magnetic material. At the microscopic level, however, the opposite alignment of spins forms a rich internal structure. In topological antiferromagnets, this internal structure leads to the possibility that the property known as the Berry phase can acquire distinct spatial textures(2,3). Here we study this possibility in an antiferromagnetic axion insulator-even-layered, two-dimensional MnBi2Te4-in which spatial degrees of freedom correspond to different layers. We observe a type of Hall effect-the layer Hall effect-in which electrons from the top and bottom layers spontaneously deflect in opposite directions. Specifically, under zero electric field, even-layered MnBi2Te4 shows no anomalous Hall effect. However, applying an electric field leads to the emergence of a large, layer-polarized anomalous Hall effect of about 0.5e(2)/h (where e is the electron charge and h is Planck's constant). This layer Hall effect uncovers an unusual layer-locked Berry curvature, which serves to characterize the axion insulator state. Moreover, we find that the layer-locked Berry curvature can be manipulated by the axion field formed from the dot product of the electric and magnetic field vectors. Our results offer new pathways to detect and manipulate the internal spatial structure of fully compensated topological antiferromagnets(4-9). The layer-locked Berry curvature represents a first step towards spatial engineering of the Berry phase through effects such as layer-specific moire potential.