Phase transition of ultrathin Bi2Se3 film sandwiched between ferromagnetic insulators

Abstract

For an ultra-thin Bi2Se3 film sandwiched between two ferromagnetic insulators (FIs), we investigate how its topological properties change with the angle between the magnetizations of the two FIs. The Chern numbers are calculated from the low-energy effective Hamiltonian for electrons in the surface states, and the bulk energy band and the edge states are simulated from the tight-binding model of a long ribbon with armchair edges on a two-dimensional honeycomb lattice, from which the topological phase of the system can be determined. It is found that with the magnetizations of the FIs varying from parallel to antiparallel, there appears a topological phase transition from the anomalous quantum Hall phase to the trivial insulating one at a critical angle.