04-329 J.M. Combes, F. Germinet
Edge and Impurity Effects on Quantization of Hall Currents (309K, .pdf) Oct 20, 04
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Abstract. We consider the edge Hall conductance and show it is invariant under perturbations located in a strip along the edge (decaying perturbations far from the edge are also allowed). This enables us to prove for the edge conductances a general sum rule relating currents due to the presence of two different media located respectively on the left and on the right half plane. As a particular interesting case we put forward a general quantization formula for the difference of edge Hall conductances in semi-infinite samples with and without a confining wall. It implies in particular that the edge Hall conductance takes its ideal quantized value under a gap condition for the bulk Hamiltonian, or under some localization properties for a random bulk Hamiltonian (provided one first regularizes the conductance; we shall discuss this regularization issue). Our quantization formula also shows that deviations from the ideal value occurs if a semi infinite distribution of impurity potentials is repulsive enough to produce current-carrying surface states on its boundary.

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