Tunable topological surface and realization of insulating massive Dirac fermion state in Bi2Te2Se with co-substitution

Abstract

The ternary topological insulator Bi₂Te₂Se is exceptional as it has a larger bulk resistivity than previously studied topological insulators. Here we explored the possibility of modifying the topological surface states and achieving the insulating massive Dirac fermion state in Bi₂Te₂Se on the basis of density functional calculations. Substitution of O for the outmost-layer Te leads to tunable surface states with an ideal Dirac cone. The co-substitution of Cr and O, as well as that of Mn and F, for the surface Bi and Te places the Dirac point inside the bulk band gap and opens a band gap at the Dirac point, hence creating the insulating massive Dirac fermion state. The co-substitution of magnetic and non-magnetic elements is a promising way of tuning the properties of topological insulators.