BCS-BEC crossover and the disappearance of FFLO-correlations in a spin-imbalanced, one-dimensional Fermi gas

TL;DR

This study numerically investigates the BCS-BEC crossover in a one-dimensional, spin-imbalanced Fermi gas, revealing the disappearance of FFLO correlations near resonance and how critical polarization varies with detuning and filling.

Contribution

It provides the first detailed numerical analysis of FFLO correlation behavior across the BCS-BEC crossover in a 1D spin-imbalanced Fermi gas.

Findings

FFLO correlations vanish below full polarization near resonance.

Critical polarization depends on detuning and filling.

Phase diagram mapped as a function of detuning and polarization.

Abstract

We present a numerical study of the one-dimensional BCS-BEC crossover of a spin-imbalanced Fermi gas. The crossover is described by the Bose-Fermi resonance model in a real space representation. Our main interest is in the behavior of the pair correlations, which, in the BCS limit, are of the Fulde-Ferrell-Larkin-Ovchinnikov type, while in the BEC limit, a superfluid of diatomic molecules forms that exhibits quasi-condensation at zero momentum. We use the density matrix renormalization group method to compute the phase diagram as a function of the detuning of the molecular level and the polarization. As a main result, we show that FFLO-like correlations disappear well below full polarization close to the resonance. The critical polarization depends on both the detuning and the filling.