Enhancement effect of mass imbalance on Fulde-Ferrell-Larkin-Ovchinnikov type of pairing in Fermi-Fermi mixtures of ultracold quantum gases

TL;DR

This paper investigates how mass imbalance in ultracold Fermi gases can significantly enhance FFLO pairing states, potentially aiding their experimental observation in three dimensions.

Contribution

It demonstrates that a large mass ratio in Fermi-Fermi mixtures can substantially promote FFLO pairing, providing new insights into phase behavior at mean-field level.

Findings

Large mass ratio enhances FFLO pairing.

Phase diagrams show increased stability of FFLO states.

Potential pathway for experimental observation of FFLO states.

Abstract

Ultracold two-component Fermi gases with a tunable population imbalance have provided an excellent opportunity for studying the exotic Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) states, which have been of great interest in condensed matter physics. However, the FFLO states have not been observed experimentally in Fermi gases in three dimensions (3D), possibly due to their small phase space volume and extremely low temperature required for an equal-mass Fermi gas. Here we explore possible effects of mass imbalance, mainly in a $^6$Li--$^{40}$K mixture, on the one-plane-wave FFLO phases for a 3D homogeneous case at the mean-field level. We present various phase diagrams related to the FFLO states at both zero and finite temperatures, throughout the BCS-BEC crossover, and show that a large mass ratio may enhance substantially FFLO type of pairing.