Large Range of Stability of Larkin-Ovchinnikov States for Imbalanced Fermi Gases in Optical Lattices

TL;DR

This paper demonstrates that Larkin-Ovchinnikov states are more stable in optical lattice systems than in free space, with a large parameter range and distinct experimental signatures, using a self-consistent theoretical approach.

Contribution

It provides the first comprehensive phase diagram for LO states in a 3D lattice Hubbard model with population imbalance, highlighting their extensive stability and detection signatures.

Findings

LO states have a larger stability range in lattices than in continuum.

Strong local polarization modulation is a signature of LO phases.

LO phases can occupy up to 80% of atoms in a trap.

Abstract

We show that Larkin-Ovchinnikov (LO) states with modulated superfluid order parameters have a considerably larger range of stability in a lattice than in the continuum. We obtain the phase diagram for the 3D cubic attractive Hubbard model with an unequal population of up and down fermions using the Bogoliubov-de Gennes fully self-consistent method. We find a strong modulation of the local polarization that should provide a distinct signature for detection of the LO phase. The shell structure in the presence of a trap generates singularities in the density at the phase boundaries and provide additional evidence for the LO phase. Depending on specific parameters, the LO ground state occurs over a large range of population imbalance, involving 80% of the atoms in the trap, and can exist up to an entropy s ~ 0.5 k_B per fermion.