Ultra-cold Fermi gases with resonant dipole-dipole interaction

TL;DR

This paper explores the unique superfluid phases in resonant dipolar Fermi gases, revealing two distinct BEC phases with different symmetries and a spontaneous time-reversal symmetry breaking near resonance.

Contribution

It introduces a theoretical analysis showing that resonant dipolar interactions produce two different BEC phases and a coexistence regime with spontaneous symmetry breaking.

Findings

Two distinct BEC phases characterized by different order parameters.

Coexistence of phases near resonance with spontaneous time-reversal symmetry breaking.

Potential experimental observation via momentum-resolved rf-spectroscopy.

Abstract

The superfluid phases in the resonant dipolar Fermi gases are investigated by the standard mean-field theory. In contrast to the crossover from Bose-Einstein condensation (BEC) to Bardeen-Cooper-Schrieffer (BCS) superfluid in the Fermi gases with the isotropic interactions, the resonant dipolar interaction leads to two completely different BEC phases of the tight-binding Fermi molecules on both sides of the resonance, which are characterized by two order parameters with the distinct internal symmetries. We point that near the resonance, the two competitive phases can coexist, and an emergent relative phase between the two order parameters spontaneously breaks the time-reversal symmetry, which could be observed in the momentum resolved rf-spectroscopy.