Ji Yuchen, Liu Zheng, Zhang Peng, Li Lun, Qi Shifei, Chen Peng, Zhang Yong, Yao Qi, Liu Zhongkai, Wang Kang L, Qiao Zhenhua, Kou Xufeng
ShanghaiTech Laboratory for Topological Physics, School of Physical Science and Technology, ShanghaiTech University, Shanghai, China 201210.
University of Chinese Academy of Sciences, Beijing, China 101408.
ACS Nano. 2022 Jan 25;16(1):1134-1141. doi: 10.1021/acsnano.1c08874. Epub 2022 Jan 10.
The quantized version of the anomalous Hall effect realized in magnetic topological insulators (MTIs) has great potential for the development of topological quantum physics and low-power electronic/spintronic applications. Here we report the thickness-tailored quantum anomalous Hall (QAH) effect in Cr-doped (Bi,Sb)Te thin films by tuning the system across the two-dimensional (2D) limit. In addition to the Chern number-related QAH phase transition, we also demonstrate that the induced hybridization gap plays an indispensable role in determining the ground magnetic state of the MTIs; namely, the spontaneous magnetization owing to considerable Van Vleck spin susceptibility guarantees the zero-field QAH state with unitary scaling law in thick samples, while the quantization of the Hall conductance can only be achieved with the assistance of external magnetic fields in ultrathin films. The modulation of topology and magnetism through structural engineering may provide useful guidance for the pursuit of other QAH-based phase diagrams and functionalities.
在磁性拓扑绝缘体（MTIs）中实现的反常霍尔效应的量子化版本，在拓扑量子物理和低功耗电子/自旋电子学应用的发展方面具有巨大潜力。在此，我们报告了通过在二维（2D）极限附近调节系统，在Cr掺杂的（Bi，Sb）Te薄膜中实现的厚度定制量子反常霍尔（QAH）效应。除了与陈数相关的QAH相变外，我们还证明了诱导的杂化能隙在确定MTIs的基态磁状态中起着不可或缺的作用；也就是说，由于可观的范弗莱克自旋磁化率导致的自发磁化保证了厚样品中具有幺正标度律的零场QAH状态，而在超薄薄膜中，霍尔电导的量子化只能在外部磁场的辅助下实现。通过结构工程对拓扑和磁性进行调制，可能为探索其他基于QAH的相图和功能提供有用的指导。
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