Finite temperature stability and dimensional crossover of exotic superfluidity in lattices

TL;DR

This study explores the stability and properties of exotic FFLO superfluid states in spin-imbalanced Fermi gases across different lattice dimensions, revealing their robustness and melting behavior at finite temperatures.

Contribution

It provides the first finite temperature phase diagram of FFLO states in anisotropic lattices, highlighting the role of dimensional crossover in stabilizing these states.

Findings

FFLO state persists up to about one third of the BCS critical temperature.

The gapless nature of FFLO is reflected in the local spectral function.

Intermediate dimensions can stabilize uniform FFLO states under harmonic confinement.

Abstract

We investigate exotic paired states of spin-imbalanced Fermi gases in anisotropic lattices, tuning the dimension between one and three. We calculate the finite temperature phase diagram of the system using real-space dynamical mean-field theory in combination with the quantum Monte Carlo method. We find that regardless of the intermediate dimensions examined, the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state survives to reach about one third of the BCS critical temperature of the spin-density balanced case. We show how the gapless nature of the state found is reflected in the local spectral function. While the FFLO state is found at a wide range of polarizations at low temperatures across the dimensional crossover, with increasing temperature we find out strongly dimensionality-dependent melting characteristics of shell structures related to harmonic confinement. Moreover, we show that intermediate dimension can help to stabilize an extremely uniform finite temperature FFLO state despite the presence of harmonic confinement.