Massive Dirac surface states in topological insulator/magnetic insulator heterostructures

Topological insulators are new states of matter with a bulk gap and robust gapless surface states protected by time-reversal symmetry. When time-reversal symmetry is broken, the surface states are gapped, which induces a topological response of the system to electromagnetic field-the topological magnetoelectric effect. In this paper we study the behavior of topological surface states in heterostructures formed by a topological insulator and a magnetic insulator. Several magnetic insulators with compatible magnetic structure and relatively good lattice matching with topological insulators Bi2Se3, Bi2Te3, Sb2Te3 are identified, and the best candidate material is found to be MnSe, an antiferromagnetic insulator. We perform first-principles calculations in Bi2Se3/MnSe superlattices and obtain the surface state band structure. The magnetic exchange coupling with MnSe induces a gap of similar to 54 meV at the surface states. In addition we tune the distance between Mn ions and the topological insulator surface to study the distance dependence of the exchange coupling. DOI: 10.1103/PhysRevB.87.085431