Phase diagram of a model for topological superconducting wires

Abstract

We calculate the phase diagram of a model for topological superconducting wires with local swave pairing, spin-orbit coupling λ and magnetic field B with arbitrary orientations. This model is a generalized lattice version of the one proposed by Lutchyn et al. [Phys. Rev. Lett. 105 077001 (2010)] and Oreg et al. [Phys. Rev. Lett. 105 177002 (2010)], who considered λ perpendicular to B. The model has a topological gapped phase with Majorana zero modes localized at the ends of the wires. We determine analytically the boundary of this phase. When the directions of the spin-orbit coupling and magnetic field are not perpendicular, in addition to the topological phase and the gapped non-topological phase, a gapless superconducting phase appear.