Topological superfluid transition induced by a periodically driven optical lattice

We propose a scenario to create a topological superfluid in a periodically driven two-dimensional square optical lattice. We study the phase diagram of a spin-orbit coupled s-wave pairing superfluid in a periodically driven two-dimensional square optical lattice. We find that a phase transition from a trivial superfluid to a topological superfluid occurs when the potentials of the optical lattices are periodically changed. The topological phase is called the Floquet topological superfluid and can host Majorana fermions.