Probing anisotropic superfluidity of rashbons in atomic Fermi gases

TL;DR

This paper theoretically explores how Rashba spin-orbit coupling induces anisotropic superfluidity in strongly interacting Fermi gases, specifically in $^{40}$K atoms, and proposes experimental probes for this phenomenon.

Contribution

It introduces the concept of rashbons as mixed singlet-triplet pairs and analyzes their role in creating anisotropic superfluidity in spin-orbit coupled Fermi gases.

Findings

Rashba spin-orbit coupling lifts spin degeneracy, leading to rashbon formation.

Anisotropic superfluidity can be detected via momentum distribution measurements.

Single-particle spectral functions reveal signatures of rashbon-induced superfluidity.

Abstract

Motivated by the prospect of realizing a Fermi gas of $^{40}$K atoms with a synthetic non-Abelian gauge field, we investigate theoretically a strongly interacting Fermi gas in the presence of a Rashba spin-orbit coupling. As the two-fold spin degeneracy is lifted by spin-orbit interaction, bound pairs with mixed singlet and triplet pairings (referred to as rashbons) emerge, leading to an anisotropic superfluid. We show that this anisotropic superfluidity can be probed via measuring the momentum distribution and single-particle spectral function in a trapped atomic $^{40}$K cloud near a Feshbach resonance.