We focus on three-component SU(3) Fermi gases loaded into a square optical lattice, with population imbalance between one component and the others.At strong coupling the system is described by the SU(3) Heisenberg model with an external field that couples to the population imbalance.We discuss the ground state at the mean-field level and then analyze the thermal fluctuations with the semiclassical Monte Carlo method.The interplay of interactions, population imbalance, and thermal fluctuations gives rise to a phase transition linked to the breaking of an emergent Ising symmetry, despite the absence of frustration.This represents another scenario of discrete symmetry breaking in low-dimensional systems with continuous symmetries.Possible implementations with cold alkaline-earth(-like) atoms are discussed.
In this paper, we study the effect of population imbalance and its interplay with pairing strength and lattice effect in atomic Fermi gases in a one-dimensional optical lattice. We compute various phase diagrams as the system undergoes BCS-BEC crossover, using the same pairing fluctuation theory as in Part I of this work [Phys. Rev. A 101, 053617 (2020)]. We find widespread pseudogap phenomena beyond the BCS regime and intermediate temperature superfluid states for relatively low population imbalances. The Fermi surface topology plays an important role in the behavior of
Tc. For large
d and/or small
t, which yield an open Fermi surface, superfluidity can be readily destroyed by a small amount of population imbalance
p. The superfluid phase, especially in the BEC regime, can exist only for a highly restricted volume of the parameter space. An open Fermi surface often leads to destruction of the superfluid ground state in the BEC regime. Due to the continuum-lattice mixing, population imbalance gives rise to a new mechanism for pair hopping, as assisted by excessive majority fermions, which may lead to significant enhancement of
Tc on the BEC side of the Feshbach resonance, and also render
Tc approaching a constant asymptote in the BEC limit, when it exists. Furthermore, we find that not all minority fermions will be paired up in BEC limit, unlike the 3D continuum case. These predictions can be tested in future experiments.