First-Principles Study of Surface States of Bi[sub 2]Te[sub 3]

Bi2Te3 is a topological insulator with time reversal symmetry possessing a single Dirac cone at a given surface. The surface states of topological insulators play a critical role in exotic physical phenomena and their applications. We investigate the surface states of thin films of Bi2Te3(111) using density-functional theory including spin-orbit coupling. Considering one to six quintuple layers (QLs) of Bi2Te3 films, we identify the surface states from calculated band structures using the decay length of the surface states and electron density plots. We show that the films of 1 and 2 QLs are too thin to hold the surface states protected topologically, and that for thicker films bands identified as surface states at (Gamma) over bar lose their surface-state features away from (Gamma) over bar. This method can be applied to other topological insulators.