Polarized Fermi gases in asymmetric optical lattices

TL;DR

This paper explores how asymmetric optical lattices influence the phase diagrams of imbalanced Fermi gases at zero temperature, revealing conditions that favor BCS or FFLO states and how external traps affect phase profiles.

Contribution

It provides an exact spectrum analysis of phase diagrams in asymmetric lattices, surpassing the Fermi-Hubbard model, and examines the effects of lattice potential and density on superfluid states.

Findings

Lattice potential enhances BCS at low densities.

FFLO state is favored at intermediate densities during dimensional crossover.

Phase profiles evolve with lattice tuning in harmonic traps.

Abstract

The zero-temperature phase diagrams of imbalanced two-species Fermi gases are investigated in asymmetric optical lattices with arbitrary potential depths, based on the exact spectrum instead of the Fermi-Hubbard model. We study the effect of lattice potentials and atomic densities to the fully paired Bardeen-Cooper-Schrieffer (BCS) state and particularly the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state. It is found that the increasing lattice potential favors BCS at low densities because of the enhanced effective coupling; whereas FFLO is favored at intermediate densities when the system undergoes a dimensional crossover. Finally using local density approximation we study the evolution of phase profile in the presence of external harmonic traps by merely tuning the lattice potentials.