Reentrant Superfluidity and Pair Density Wave in Single Component Dipolar Fermi Gases

TL;DR

This paper investigates the superfluidity of single component dipolar Fermi gases, revealing re-entrant behavior of the transition temperature and the emergence of a pair density wave state due to anisotropic long-range interactions.

Contribution

It introduces a pairing fluctuation theory to describe superfluidity in dipolar Fermi gases, uncovering re-entrant superfluidity and a novel pair density wave phase.

Findings

Re-entrant superfluid transition temperature as a function of interaction strength.

Emergence of pair density wave state at intermediate interactions.

Analysis of superfluid density and thermodynamics across the BCS-BEC crossover.

Abstract

We study the superfluidity of single component dipolar Fermi gases in three dimensions within a pairing fluctuation theory. The transition temperature $T_{c}$ for the dominant $p_z$ wave superfluidity exhibits a remarkable re-entrant behavior as a function of the pairing strength induced by the dipole-dipole interaction (DDI), which leads to an anisotropic pair dispersion. The anisotropy and the long range nature of the DDI cause $T_c$ to vanish for a narrow range of intermediate interaction strengths, where a pair density wave state emerges as the ground state. The superfluid density and thermodynamics below $T_{c}$, along with the density profiles in a harmonic trap, are investigated as well, throughout the BCS-BEC crossover. Implications for experiments are discussed.