Quantum transport and absence of Anderson localization in strong and weak topological insulators

by Jens Bardarson (University of California Berkeley)

Wednesday 8 Feb 2012, 09:00 → 09:50 Europe/Stockholm

122:026

A single Dirac fermion, realized at the surface of a 3D strong topological insulator, can not be localized by time reversal symmetric disorder. Rather, the surface always flows into a symplectic metal phase characterized by weak anti-localization. This absence of Anderson localization in the surface is one of the characterizing features of a topological insulator. The surface of a weak topological insulator, however, does not have a topological protection against Anderson localization yet, surprisingly, manages to avoid it under general conditions. A metal-insulator transition is only obtained in the presence of a time reversal symmetric mass. We demonstrate this, and the resulting two parameter scaling, by a numerical solution of the Dirac equation in the presence of Gaussian disorder. We briefly discuss the role of a topological term in the underlying field theory of diffusion and how it can be used, together with the demonstrated absence of localization, to construct the perodic table of topological insulators.