Superfluid-insulator transitions of the Fermi gas with near-unitary interactions in a periodic potential

TL;DR

This paper investigates the quantum phase transition between superfluid and insulator states in a Fermi gas with near-unitary interactions within a periodic potential, providing universal ratios and insights relevant to experiments.

Contribution

It introduces a model analyzing the superfluid-insulator transition at unitarity in a periodic potential, calculating universal ratios at large N, and connecting insulator types to experimental observations.

Findings

Identifies a second-order quantum phase transition at a critical potential Vc.

Calculates the universal ratio Vc m a^2 / h^2 at N=infinity.

Describes the insulator as interpolating between band and Mott insulators.

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, 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=Vc. We compute the universal ratio Vc m a^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.