The quantum anomalous Hall effect in a topological insulator thin film —The role of magnetic disorder

Abstract

The quantum anomalous Hall (QAH) effect in a topological insulator thin film is investigated theoretically by using the nonequilibrium Green function method. We use the tight-binding model of a six-terminal topological thin-film Hall bar and focus on the effects of magnetic disorder and electron-hole asymmetry. In the QAH regime, when disorder is considered the electron transmissions contributed by the edge states are suppressed and other transmissions are enhanced. Under proper disorder strength, within an interval around the neutral point, the Hall conductance is quantized and the longitudinal conductance is zero. At the interval edges, decreases quickly and peaks. With the presence of electron-hole asymmetry, the plateau of shifts because the neutral point is shifted. These results are in good agreement with the experimental reports (Chang C. Z. et al., Science 340 (2013) 167). When the distance between longitudinal terminals is longer, peaks are lower and drops sharply at the plateau edge. The effect of a second type of disorder is studied and similar results are obtained.