Reentrant Fulde-Ferrell-Larkin-Ovchinnikov superfluidity in the honeycomb lattice

TL;DR

This paper investigates the emergence of reentrant FFLO superfluid phases in a honeycomb lattice with imbalanced ultracold Fermi gases, highlighting unconventional pairing behavior influenced by van Hove singularities.

Contribution

It demonstrates the existence of reentrant FFLO phases in the honeycomb lattice and explores their unique momentum behavior under magnetic fields, a novel insight in this context.

Findings

Reentrant FFLO phase can occur without a BCS precursor.

The Cooper pair momentum exhibits atypical changes in magnitude and direction.

Van Hove singularities influence the stability of the FFLO phase.

Abstract

We study superconducting properties of population-imbalanced ultracold Fermi mixtures in the honeycomb lattice that can be effectively described by the spin-imbalanced attractive Hubbard model in the presence of a Zeeman magnetic field. We use the mean-field theory approach to obtain ground state phase diagrams including some unconventional superconducting phases such as the Fulde--Ferrell--Larkin--Ovchinnikov (FFLO) phase. We show that this phase is characterized by atypical behaviour of the Cooper pairs total momentum in the external magnetic field. We show that the momentum changes its value as well as direction with change of the system parameters. We discuss the influence of van Hove singularities on the possibility of the reentrant FFLO phase occurrence, without a BCS precursor.