Robust surface state of intrinsic topological insulator Bi _2Te _2Se thin films: A first-principles study

摘要

Bi _2Te _2Se, a ternary tetradymite compound, has recently been identified to be a three-dimensional topological insulator. In this paper, we theoretically study the electronic structures of bulk and thin films of Bi _2Te _2Se employing spinorbit coupling (SOC) self-consistently with density-functional theory. It is found that SOC plays an important role in determining the electronic properties of Bi 2Te 2Se. A finite bandgap opens up in the surface states of Bi _2Te _2Se thin films due to the hybridization of the top and bottom surface states of films. The intrinsic Bi _2Te _2Se thin films of three or more quintuple layers exhibit a robust topological nature of electronic structure with the Fermi energy intersecting the Dirac cone of the surface states only once between time-reversal-invariant momenta. These characteristics of Bi _2Te _2Seare similar to the topological behavior of Bi _2Te _3, promising a variety of potential applications in nanoelectronics and spintronics.