Population imbalanced Fermi gases in quasi two dimensions

TL;DR

This paper explores the phase diagram of population imbalanced Fermi gases in quasi-2D, revealing how interlayer tunneling influences superfluid stability, phase transitions, and the emergence of polarized superfluid and FFLO phases.

Contribution

It provides a comprehensive analysis of the effects of weak interlayer tunneling on superfluid phases and phase transitions in quasi-2D imbalanced Fermi gases across the BCS-BEC crossover.

Findings

Superfluid phase stabilizes with decreased tunneling.

Tunneling controls the superfluid-normal first order transition.

A tunneling-induced polarized superfluid appears in the BEC regime.

Abstract

We study s-wave pairing of population imbalanced Fermi atoms in quasi two dimensions using a mean field theory. At zero temperature, we map out the phase diagram in the entire Bardeen, Cooper and Schrieffer-Bose Einstein condensation (BCS-BEC) crossover region by investigating the effect of weak atom tunneling between layers. We find that the superfluid phase stabilizes as one decreases the atom tunneling between layers. This allows one to control the superfluid-normal first order phase transition by tuning a single experimental parameter. Further, we find that a tunneling induced polarized superfluid phase appears in a narrow parameter region in the BEC regime. At Finite temperatures, we use a Landau-Ginzberg functional approach to investigate the possibility of spatially inhomogeneous Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) phase in the weakly interacting BCS limit near the tricritical point of spatially homogenous superfluid, FFLO, and normal phases. We find that the normal-FFLO phase transition is first order transition as opposed to the continues transition predicted in zero temperature theories.