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Topological Anderson insulator phenomena

We study the nature of the disorder-induced quantized conductance, i.e., the phenomena of topological Anderson insulator (TAI) induced in HgTe/CdTe semiconductor quantum well. The disorder effect in several different systems where anomalous Hall effect exist, is numerically studied using the tight-binding Hamiltonian. It is found that the TAI phenomena also occur in the modified Dirac model where the quadratic corrections $k^2σ_z$ is included and electron-hole symmetry is kept. It also occurs in the graphene system with the next nearest-neighbor coupling and staggered sublattice potential. Comparison between the localization lengths of the 2D ribbon and 2D cylinder clearly reveals the topological nature of this phenomena. Furthermore, analysis on the local current density in anomalous quantum Hall systems where the TAI phenomena can or can not arise reveals the nature of TAI phenomena: the bulk state is killed drastically and only the robust edge state survives in a moderate disorder. When the edge state is robust enough to resist the strong disorder that can completely kills the bulk state, TAI phenomena arise.