Koji Kobayashi, Tomi Ohtsuki, Ken-Ichiro Imura
Robustness against disorder is a defining property of the topological quantum phenomena. Here, we highlight unexpected robustness of transport characteristics found in a lattice model of disordered three-dimensional Z2 topological insulator. We have studied numerically the global phase diagram of this model yielding both the weak and strong topological insulator (WTI and STI) phases to quantify how they collapse as a function of disorder. We have found that the average two-terminal conductance is quantized both in the bulk and slab geometries. This indicates that not only the surface Dirac cones in the STI and WTI phases but also bulk Dirac cones emergent at the phase boundaries exhibit robustness against disorder. We have also studied the Lyapunov exponents in the quasi one-dimensional geometry to verify that both the STI and WTI phases are indeed stable up to a finite strength of disorder.
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http://arxiv.org/abs/1210.4656
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