Symmetry-protected topological phases have gapless surface (edge) states. These states are robust against any single-body perturbation that has the symmetry, as long as the gap in the bulk spectrum is not closed. Recently, it is found that these gapless surface states can be gapped when many-body interaction is included. In this talk, I will discuss what kind of many-body interaction opens a gap in the surface of topological superconductor without breaking its symmetry.

Time reversal symmetric topological superconductor carries gapless Majorana fermion on the surface. I will discuss the “Coupled Wire Model” which we built to mimic the massless Majoranas in the surface. I will talk about how the explicit many-body inter-wire interaction, that we introduced, preserves time reversal symmetry but opens a gap in the surface spectrum. I will also discuss the resulting gapped surface carrying non-trivial topological order evident from the anyon structure that we find.