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

摘要

Ultracold two-component Fermi gases with a tunable population imbalance haveprovided an excellent opportunity for studying the exoticFulde-Ferrell-Larkin-Ovchinnikov (FFLO) states, which have been of greatinterest in condensed matter physics. However, the FFLO states have not beenobserved experimentally in Fermi gases in three dimensions (3D), possibly dueto their small phase space volume and extremely low temperature required for anequal-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 a3D homogeneous case at the mean-field level. We present various phase diagramsrelated to the FFLO states at both zero and finite temperatures, throughout theBCS-BEC crossover, and show that a large mass ratio may enhance substantiallyFFLO type of pairing.