Phase transitions in quasi-one dimensional system with unconventional superconductivity

TL;DR

This paper explores the phase diagram of a quasi-one dimensional fermionic system with population imbalance, revealing both conventional and unconventional superconducting states, including the FFLO phase, under varying chemical potential and magnetic field.

Contribution

It provides a detailed analysis of the ground state phases and transition orders in an attractive Hubbard model with Zeeman field, highlighting the existence of FFLO states in such systems.

Findings

Identification of BCS and FFLO phases in the phase diagram.

Determination of transition orders between different superconducting states.

Behavior of order parameters across phase transitions.

Abstract

The paper is devoted to a study of superconducting properties of population-imbalanced fermionic mixtures in quasi-one dimensional optical lattices. The system can be effectively described by the attractive Hubbard model with the Zeeman magnetic field term. We investigated the ground state phase diagram of the model as a function of the chemical potential and the magnetic field. The ground state of the system exhibits the conventional BCS-type superconductivity as well as the unconventional so-called Fulde-Ferrell-Larkin-Ovchinnikov state, in which the total momentum of Cooper pairs is non-zero. We determine the orders of transitions as well as the behavior of order parameters with a change of the model parameters.