Superfluidity of interacting fermions in optical lattices: Interplay of population imbalance, dimensionality, and lattice-continuum mixing

In this talk, I will discuss the superfluid behavior of ultracold atomic Fermi gases in 1D and 2D optical lattices (OL), subject to a short range pairing interaction, and show the highly unusual behavior as a consequence of the interplay between population imbalance, dimensionality and more importantly lattice-continuum mixing. These systems are different from pure 3D continuum or 3D lattices, in that each lattice "site" now contains many fermions. Using a pairing fluctuation theory, we demonstrate that this feature leads to unexpected enhancement of pair hopping in the presence of population imbalace and thus possible enhancement of Tc on the BEC side of the unitary limit. For 1DOL, the superfluid phase exists only for a very limited range of parameters, and the truncated momentum space in the lattice dimension in combination with the enhanced pair hopping may give rise to enhance Tc in the BEC regime, with an constant BEC asymptote. For 2DOL, the further truncated momentum space helps to strongly suppress pairing fluctuation contributions to the pseudogap, so that Tc gradually approaches its high mean-field value in the deep BEC regime.

Reference: arXiv:1904.09576.