Flow enhanced pairing and other novel effects in Fermi gases in synthetic gauge fields

TL;DR

This paper theoretically explores how synthetic gauge fields in Fermi gases induce novel phenomena such as flow-enhanced pairing, bound states at finite momentum, and resonance-like scattering effects, revealing new regimes of superfluidity and normal states.

Contribution

It introduces the concept of flow-enhanced pairing and identifies resonance-like scattering effects caused by synthetic gauge fields in Fermi gases.

Findings

Bound states appear at nonzero momentum for certain scattering lengths.

Synthetic gauge fields induce resonance-like features in scattering continuum.

Flow-enhanced superfluidity occurs at finite center of mass momentum.

Abstract

Recent experiments on fermions in synthetic gauge fields result in systems with a spin-orbit coupling along one spatial axis, a detuning field, and a Zeeman field. We show theoretically that the presence of all three results in interesting and unusual phenomena in such systems in the presence of a contact singlet attraction between the fermions (described by a scattering length). For two particles, bound states appear over certain range of the centre of mass momenta when a critical positive scattering length is attained, with the deepest bound state appearing at a nonzero centre of mass momentum. For the centre of mass momenta without a bound state, the gauge field induces a resonance like feature in the scattering continuum resulting in a large scattering phase shift. For many particles, we demonstrate that the system, in a parameter range, shows flow enhanced pairing, i.e., a more robust superfluid at finite centre of mass momentum. Yet another regime of parameters offers the opportunity to study strongly interacting normal states of spin-orbit coupled fermionic systems utilizing the resonance like feature induced by the synthetic gauge field.