First time to pose a question here. It's a Hamiltonian appears in this paper https://journals.aps.org/rmp/abstract/10.1103/RevModPhys.87.137
The equation (71) $$ h_0(q) = v q\sigma^y+m\sigma^x-\mu $$ is the Bloch Hamiltonian for the low energy edge mode of a 2D topological insulator, where v is the mode velocity and m is the the x component of the magnetic order induced by the proximate magnetic insulator, as described by the author. Could anyone explain this point to me? Thanks in advance.