Superfluid density of the ultra-cold Fermi gas in optical lattices

Abstract

In this paper, we study the superfluid density of the two-component Fermi gas in optical lattices with population imbalance. Three different types of phases, the BCS state (Bardeen, Cooper and Schrieffer), the FFLO state (Fulde, Ferrel, Larkin and Ovchinnikov) and the Sarma state, are considered. We show that the FFLO superfluid density differs from the BCS/Sarma superfluid density in an important way. Although there are dynamical instabilities in the FFLO phase, when the interaction is strong or densities are high, the FFLO phase is found to be stable on the weak coupling limit.