Topological surface states of Bi2Se3 coexisting with Se vacancies

Although topological surface states are known to be robust against nonmagnetic surface perturbations, their band dispersions and spatial distributions are still sensitive to surface defects. Taking Bi2Se3 as an example, we demonstrate that Se vacancies modify the surface band structures considerably. When large numbers of Se vacancies exist on the surface, topological surface states may sink down from the first to the second quintuple layer and get separated from the vacancies. We simulated scanning tunnelling microscopy images to distinguish surfaces with Se and Bi terminations. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) Topological surface states are known to be robust against local defects such as vacancies and dangling bonds. In this Letter, another aspect of the topological protection is demonstrated. On the Bi2Se3 surface, topological surface states are found to sink down from the outer surface to the inner atomic layers, separating themselves away from defects, if a large number of Se vacancies exists on the surface.