Thickness-Driven Quantum Anomalous Hall Phase Transition in Magnetic Topological Insulator Thin Films,ACS Nano

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Thickness-Driven Quantum Anomalous Hall Phase Transition in Magnetic Topological Insulator Thin Films
ACS Nano ( IF 15.8 ) Pub Date : 2022-01-10 , DOI: 10.1021/acsnano.1c08874
Yuchen Ji _{1,

2} , Zheng Liu ₃ , Peng Zhang ₄ , Lun Li _{2,

5} , Shifei Qi _{3,

6} , Peng Chen _{2,

5} , Yong Zhang _{2,

5} , Qi Yao ₁ , Zhongkai Liu ₁ , Kang L Wang ₄ , Zhenhua Qiao ₃ , Xufeng Kou _{1,

5}

Affiliation

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)₂Te₃ 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.

中文翻译：

磁性拓扑绝缘体薄膜中厚度驱动的量子反常霍尔相变

在磁拓扑绝缘体 (MTI) 中实现的异常霍尔效应的量化版本对于拓扑量子物理学和低功率电子/自旋电子应用的发展具有巨大潜力。_{在这里，我们报告了 Cr 掺杂 (Bi,Sb) 2} Te ₃中的厚度定制的量子反常霍尔 (QAH) 效应通过在二维（2D）限制上调整系统来制备薄膜。除了与陈数相关的 QAH 相变外，我们还证明了诱导杂交间隙在确定 MTI 的地磁状态中起着不可或缺的作用。即，由于相当大的 Van Vleck 自旋磁化率导致的自发磁化保证了厚样品中具有单一比例定律的零场 QAH 状态，而霍尔电导的量子化只能在超薄膜中的外部磁场的帮助下实现。通过结构工程对拓扑和磁性的调制可以为追求其他基于 QAH 的相图和功能提供有用的指导。

更新日期：2022-01-25

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