Phases of attractive spin-imbalanced fermions in square lattices

TL;DR

This paper investigates the stability and structure of various ground-state phases of spin-imbalanced attractive fermions in square lattices, revealing unidirectional LO phases and a robust supersolid phase through Hartree-Fock-Bogoliubov analysis.

Contribution

It systematically characterizes the symmetry and structure of phases, including the discovery of unidirectional LO and supersolid phases, considering effects of commensuration and Fermi surface reconstruction.

Findings

Identification of unidirectional LO-type phases

Existence of a robust diagonally directed supersolid phase

Analysis of Fermi surface reconstruction mechanisms

Abstract

We determine the relative stability of different ground-state phases of spin-imbalanced popula- tions of attractive fermions in square lattices. The phases are systematically characterized by the symmetry of the order parameter and the real- and momentum-space structures using Hartree- Fock-Bogoliubov theory. We find several type of unidirectional Larkin-Ovchinikov-type phases. We discuss the effect of commensuration between the ordering wave vector and the density imbalance, and describe the mechanism of Fermi surface reconstruction and pairing for various orders. A robust supersolid phase is shown to exist when the ordering wave vector is diagonally directed.