Vacancy-induced bound states in topological insulators.

We present an exact solution of a modified Dirac equation for topological insulator in the presence of a hole or vacancy to demonstrate that vacancies can induce bound states in the band gap of topological insulators. They arise due to the Z2 classification of time-reversal invariant insulators. Coexistence of the in-gap bound states and the edge or surface states in topological insulators suggests that imperfections may affect transport properties of topological insulators via additional bound states near the system boundary. [ABSTRACT FROM AUTHOR]