Quantum phases of Fermi-Fermi mixtures in optical lattices

TL;DR

This paper explores the rich quantum phase diagram of Fermi-Fermi mixtures in optical lattices, revealing novel insulating phases and the transition to strongly interacting Bose-Fermi mixtures in the molecular limit.

Contribution

It provides a comprehensive analysis of the ground state phases, including insulating states, in Fermi-Fermi mixtures within optical lattices, highlighting differences from homogeneous systems.

Findings

Identification of insulating phases such as BMI, FPI, and BFC.

Reduction to strongly interacting Bose-Fermi mixtures in the molecular limit.

Discovery of phase-separated and checkerboard phases in optical lattices.

Abstract

The ground state phase diagram of Fermi-Fermi mixtures in optical lattices is analyzed as a function of interaction strength, population imbalance, filling fraction and tunneling parameters. It is shown that population imbalanced Fermi-Fermi mixtures reduce to strongly interacting Bose-Fermi mixtures in the molecular limit, in sharp contrast to homogeneous or harmonically trapped systems where the resulting Bose-Fermi mixture is weakly interacting. Furthermore, insulating phases are found in optical lattices of Fermi-Fermi mixtures in addition to the standard phase-separated or coexisting superfluid/excess fermion phases found in homogeneous systems. The insulating states can be a molecular Bose-Mott insulator (BMI), a Fermi-Pauli insulator (FPI), a phase-separated BMI/FPI mixture or a Bose-Fermi checkerboard (BFC).