Tuning the Dirac cone of the topological insulator Bi₂Te₃ thin films by substitutional nonmagnetic atoms

Based on first‐principles calculations, it is found that the Dirac cone of Bi₂Te₃ film, which is buried in the bulk valence bands, can be tuned by the substitutional nonmagnetic atoms. It is found that substituting the Bi layer at the two ends of Bi₂Te₃ films with group III atoms Al, Ga, In and Tl, which have lower electronegativity than Bi atoms, can lead to an isolated Dirac cone with the Dirac point shifted into the bulk band gap and located on the Fermi level. Substituting the more electronegative Se, S and O atoms for Te atoms at the top and bottom layers of Bi₂Te₃ film, only the most electronegative O atoms give rise to a nearly ideal Dirac cone. The charge distribution of the resulting isolated Dirac point state is concentrated at the Te layers facing the van der Waals layers and vanishes in the middle of the quintuple layers