Topological superfluid state of fermions on a p-band optical square lattice

In this paper we study an interacting mixture of ultracold spinless fermions on the s band and bosons on the p band in a 2D square optical lattice, of which the effective model is reduced to a p-band fermionic system with nearest-neighbor attractive interaction. From this effective p-band model, we find a translation symmetry protected Z(2) topological superfluid that is characterized by a special fermion parity pattern at high-symmetry points in momentum space k = (0,0), (0, pi), (pi, 0), (pi, pi). Such Z(2) topological superfluid supports the robust Majorana edge modes and a new type of low-energy excitation-(supersymmetric) Z(2) link excitation.