Effects of surface modification on the properties of topological surface states in Bi2Se3

The effects of surface modification on the topological surface states in Bi2Se3 have been studied using first-principles calculations. Although surface modification cannot change the topological order, however, the spin polarization, dispersion of topological surface bands and the position of Dirac points are altered. All the studied surface modifications can push Dirac cone upwards effectively. Bi-capped surface can attract the quantum well states into bulk band gap, forming new Dirac cone at M¯ point. Both Bi-capped and Se-removed surface can slightly enhance spin polarization of topological surface states, while flatten the energy dispersion of the topological surface bands above Dirac point. -- Highlights: ► Effects of defects on topological surface states are studied with first principles. ► All the defects can shift Dirac cone upwards. ► Bi-capped surface can form new anisotropic Dirac cones at M¯ points. ► Both Bi-capped and Se-removed surfaces can enhance spin polarization.