Superfluid-Insulator Transitions of the Fermi Gas with Near-Unitary Interactions in a Periodic Potential

Abstract

We consider spin-1/2 fermions of mass m with interactions near the unitary limit. In an applied periodic potential of amplitude V and period a(L), and with a density of an even integer number of fermions per unit cell, there is a second-order quantum phase transition between superfluid and insulating ground states at a critical V = V(c). We compute the universal ratio V(c)ma(L)(2)/h(2) at N = infinity in a model with Sp(2N) spin symmetry. The insulator interpolates between a band insulator of fermions and a Mott insulator of fermion pairs. We discuss implications for recent experiments.