Antiferromagnetism and superfluidity of a dipolar Fermi gas in a 2D optical lattice

TL;DR

This paper explores the complex phase diagram of a dipolar Fermi gas in a 2D optical lattice, revealing the competition between antiferromagnetism and various superfluid states influenced by filling factor and interaction strength.

Contribution

It introduces a detailed analysis of phase transitions and order parameters in a dipolar Fermi gas, highlighting the emergence of different superfluid symmetries and antiferromagnetic order at zero temperature.

Findings

Antiferromagnetic order is favored at half filling.

Superfluid states with d-wave, extended s-wave, or mixed symmetries appear at lower fillings.

A phase-separated region exists between magnetic and superfluid phases.

Abstract

In a dipolar Fermi gas, the dipole-dipole interaction between fermions can be turned into a dipolar Ising interaction between pseduospins in the presence of an AC electric field. When trapped in a 2D optical lattice, such a dipolar Fermi gas has a very rich phase diagram at zero temperature, due to the competition between antiferromagnetism and superfluidity. At half filling, the antiferromagnetic state is the favored ground state. The superfluid state appears as the ground state at a smaller filling factor. In between there is a phase-separated region. The order parameter of the superfluid state can display different symmetries depending on the filling factor and interaction strength, including d-wave ($d$), extend s-wave ($xs$), or their linear combination ($xs+i\times d$). The implication for the current experiment is discussed.