Spin excitonic and diffusive modes in superfluid Fermi liquids

TL;DR

This paper investigates how p-wave spin interactions affect collective excitations in superfluid Fermi liquids, revealing new exciton or diffusive modes and their impact on neutrino emission in neutron stars.

Contribution

It introduces the role of p-wave spin interactions in creating new collective modes and evaluates relevant Landau parameters across various Fermi systems.

Findings

Existence of exciton and diffusive modes depending on interaction sign

Interaction modifies pair-breaking phase space singularity

Impacts neutrino emissivity in neutron star matter

Abstract

A role of a particle-particle p-wave spin interaction in Fermi liquids with s-wave pairing is studied. Depending on the sign of the interaction there arises either the new exciton collective mode below the pair-breaking threshold or the diffusive excitation mode above the threshold. The Landau parameters which control the interaction strength are evaluated for various systems: the dilute fermion gases, degenerate electron liquid, metals, atomic nuclei and neutron matter. The interaction removes also the square-root singularity in the phase space of pair breaking processes. It is shown how these effects influence the neutrino emissivity in the neutron Cooper-pair recombinations in neutron stars.