Monday, July 1, 2013

1306.6748 (Hai-Zhou Lu et al.)

Quantum Transport in Magnetic Topological Insulator Thin Films    [PDF]

Hai-Zhou Lu, An Zhao, Shun-Qing Shen
The experimental observation of the quantum anomalous Hall effect was recently reported in magnetically doped topological insulator thin films [Chang \emph{et al}., Science 340, 167 (2013)]. We present a quantum transport theory for thin films of magnetic topological insulators, based on an effective model with broken particle-hole and structure inversion symmetries. We calculated the longitudinal and Hall conductances, which are in good agreement with experimental data, where there was a sudden drop in the Hall conductance on the positive gate voltage side of the quantized plateau, accompanied by a peak in the longitudinal conductance. We show that this behavior originates from a topologically nontrivial band, which has concentrated Berry curvature and a local maximum in group velocity near its band edge. In the presence of the substrate-induced structure inversion asymmetry, the bands closest to the quantized plateau are always topologically nontrivial.
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