Universal relations and normal phase of an ultracold Fermi gas with coexisting $s$- and $p$-wave interactions

TL;DR

This paper investigates the universal thermodynamic relations of a two-component ultracold Fermi gas with coexisting s- and p-wave interactions, revealing unique behaviors and abrupt energy changes near p-wave resonances.

Contribution

It introduces a framework for understanding universal relations in systems with simultaneous s- and p-wave interactions, highlighting their combined effects on thermodynamics.

Findings

Universal relations are additive over scattering channels.

Contacts associated with s- and p-wave interactions behave differently when coexisting.

Interaction energy exhibits abrupt changes near p-wave resonances.

Abstract

We study the universal relations and normal-phase thermodynamics of a two-component ultracold Fermi gas with coexisting $s$- and $p$-wave interactions. Due to the orthogonality of two-body wave functions of different scattering channels, the universal thermodynamic relations of the system appear to be direct summations of contributions from each partial-wave scattering channels. These universal relations are dictated by a set of contacts, which can be associated with either $s$- or $p$-wave interactions. Interestingly, due to the interplay of $s$- and $p$-wave interactions on the many-body level, the contacts, and hence all the relevant thermodynamic quantities, behave differently from those with only $s$- or $p$-wave interactions. These are manifest in our numerical calculations based on second-order virial expansions for $^{40}$K atoms under typical experimental parameters. A particularly interesting finding is that, due to the coexistence of $s$- and $p$-wave scatterings, the interaction energy of the repulsive branch features abrupt changes across the $p$-wave resonances. Our results can be readily checked experimentally for $^{40}$K atoms near the $198$G $p$-wave Feshbach resonance, where multiple partial-wave scatterings naturally coexist.