Robustness of the electronic structure and charge transfer in topological insulator Bi2Te2Se and Bi2Se2Te thin films under an external electric field
Using first-principles calculations based on density functional theory, we systematically investigated the electronic properties and charge transfer of topological insulator Bi2Te3−xSex thin films under an external electric field. As the selenium content in Bi2Te3−xSex thin films increases, the band gap is gradually opened, with changes in the charge distribution. In addition, the experimentally stable Bi2Te2Se and Bi2Se2Te thin films are extremely robust under vertical electric fields up to 0.2 V Å−1. The electronic structures of Bi2Te2Se and Bi2Se2Te thin films are insensitive to the electric fields and exhibit only a Rashba-like splitting pattern near the Fermi level. Remarkably, the charge transfer in Bi2Te2Se and Bi2Se2Te thin films under an external electric field is suppressed. We found that the robustness characteristic is inextricably linked to the strong covalent bonding of tellurium and bismuth atoms. These results indicated that Bi2Te2Se and Bi2Se2Te thin films are robust to the internal electrical field during growth on the substrate, which is beneficial for experimental studies as well as for the potential applications of spintronic devices.