Superfluid and insulating phases of fermion mixtures in optical lattices

TL;DR

This paper maps out the diverse ground state phases of fermion mixtures in optical lattices, revealing superfluid, insulating, and mixed phases depending on interaction and filling factors, with implications for quantum simulation.

Contribution

It introduces a comprehensive phase diagram for fermion mixtures in optical lattices, identifying new insulating phases and their relation to known atomic Bose and Fermi systems.

Findings

Identification of molecular Bose-Mott insulator (BMI) phase.

Discovery of Fermi-Pauli (band) insulator (FPI) phase.

Existence of Bose-Fermi checkerboard and phase-separated phases.

Abstract

The ground state phase diagram of fermion mixtures in optical lattices is analyzed as a function of interaction strength, fermion filling factor and tunneling parameters. In addition to standard superfluid, phase-separated or coexisting superfluid/excess-fermion phases found in homogeneous or harmonically trapped systems, fermions in optical lattices have several insulating phases, including a molecular Bose-Mott insulator (BMI), a Fermi-Pauli (band) insulator (FPI), a phase-separated BMI/FPI mixture or a Bose-Fermi checkerboard (BFC). The molecular BMI phase is the fermion mixture counterpart of the atomic BMI found in atomic Bose systems, the BFC or BMI/FPI phases exist in Bose-Fermi mixtures, and lastly the FPI phase is particular to the Fermi nature of the constituent atoms of the mixture.