Anomalous finite size effects on surface states in the topological insulator Bi2Se3

We study how the surface states in the strong topological insulator Bi2Se3 are influenced by finite size effects and compare our results with those recently obtained for two-dimensional topological insulator HgTe. We demonstrate two important distinctions: (i) contrary to HgTe, the surface states in Bi2Se3 display a remarkable robustness towards decreasing the width L down to a few nm thus ensuring that the topological surface states remain intact and (ii) the gapping due to the hybridization of the surface states features an oscillating exponential decay as a function of L in Bi2Se3 in sharp contrast to HgTe. Our findings suggest that Bi2Se3 is suitable for nanoscale applications in quantum computing or spintronics. Also, we propose a way to experimentally detect both of the predicted effects.