Department of Physics, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
Phys Rev Lett. 2013 Oct 4;111(14):146802. doi: 10.1103/PhysRevLett.111.146802. Epub 2013 Oct 2.
The experimental observation of the long-sought quantum anomalous Hall effect was recently reported in magnetically doped topological insulator thin films [Chang et al., Science 340, 167 (2013)]. An intriguing observation is a rapid decrease from the quantized plateau in the Hall conductance, accompanied by a peak in the longitudinal conductance as a function of the gate voltage. Here, we present a quantum transport theory with an effective model for magnetic topological insulator thin films. The good agreement between theory and experiment reveals that the measured transport originates from a topologically nontrivial conduction band which, near its band edge, has concentrated Berry curvature and a local maximum in group velocity. The indispensable roles of the broken structure inversion and particle-hole symmetries are also revealed. The results are instructive for future experiments and transport studies based on first-principles calculations.
最近，在磁性掺杂拓扑绝缘体薄膜中观察到了长期以来一直寻求的量子反常霍尔效应[Chang 等人，《科学》340, 167 (2013)]。一个有趣的观察结果是，霍尔电导的量子平台迅速下降，同时纵向电导作为门电压的函数出现峰值。在这里，我们提出了一个具有磁性拓扑绝缘体薄膜有效模型的量子输运理论。理论与实验的良好吻合表明，所测量的输运起源于拓扑非平凡的导带，在其能带边缘附近，具有集中的 Berry 曲率和群速度的局部最大值。还揭示了结构反转和粒子-空穴对称性被破坏的不可或缺的作用。这些结果对基于第一性原理计算的未来实验和输运研究具有指导意义。
