Fermion superfluid with hybridized $s$- and $p$-wave pairings

TL;DR

This paper proposes and analyzes a new fermion superfluid state with hybridized s- and p-wave pairings in ultracold Fermi gases, revealing stable coexistence, unique momentum-space patterns, and measurable contacts, expanding the understanding of pairing mechanisms.

Contribution

It introduces a stable hybridized s- and p-wave superfluid state in ultracold Fermi gases with coexisting interactions, and discusses its experimental signatures and implications.

Findings

Stable hybridized superfluid over a broad parameter range

Induction of p-wave pairing in non-p-wave interacting species

Measurable s- and p-wave contacts from momentum distribution

Abstract

Ever since the pioneering work of Bardeen, Cooper and Schrieffer in the 1950s, exploring novel pairing mechanisms for fermion superfluids has become one of the central tasks in modern physics. Here, we investigate a new type of fermion superfluid with hybridized $s$- and $p$-wave pairings in an ultracold spin-1/2 Fermi gas. Its occurrence is facilitated by the co-existence of comparable $s$- and $p$-wave interactions, which is realizable in a two-component $^{40}$K Fermi gas with close-by $s$- and $p$-wave Feshbach resonances. The hybridized superfluid state is stable over a considerable parameter region on the phase diagram, and can lead to intriguing patterns of spin densities and pairing fields in momentum space. In particular, it can induce a phase-locked $p$-wave pairing in the fermion species that has no $p$-wave interactions. The hybridized nature of this novel superfluid can also be confirmed by measuring the $s$-wave and $p$-wave contacts, which can be extracted from the high-momentum tail of the momentum distribution of each spin component. These results enrich our knowledge of pairing superfluidity in Fermi systems, and open the avenue for achieving novel fermion superfluids with multiple partial-wave scatterings in cold atomic gases.