Brian Skinner, B. I. Shklovskii
We study the disorder potential induced by random Coulomb impurities at the surface of a topological insulator (TI). We use a simple model in which positive and negative impurities are distributed uniformly through the bulk of the TI, and we derive the magnitude of the disorder potential at the TI surface using a self-consistent theory based on the Thomas-Fermi approximation for screening by the Dirac mode. Simple formulas are presented for the mean squared potential both at the Dirac point and far from it. We also derive an expression for the autocorrelation function for the potential at the surface and show that it has an unusually slow decay, which can be used to verify the bulk origin of disorder. Our theory is compared to results from a numerical simulation and found to be in close agreement.
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http://arxiv.org/abs/1212.6653
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