Condensate of excitations in moving superfluids

TL;DR

This paper explores the theoretical possibility of excitations condensing at non-zero momentum in moving superfluids, with implications for various bosonic and fermionic systems, including superfluid helium, neutron stars, and superconductors.

Contribution

It introduces a phenomenological framework for describing the condensation of excitations with non-zero momentum in superfluids at various temperatures.

Findings

Order parameters for the condensates are derived.

Critical temperatures and velocities are identified.

Potential applications to astrophysical and condensed matter systems are discussed.

Abstract

A possibility of the condensation of excitations with a non-zero momentum in rectilinearly moving and rotating superfluid bosonic and fermionic (with Cooper pairing) media is considered in terms of a phenomenological order-parameter functional at zero and non-zero temperature. The results might be applicable to the description of bosonic systems like superfluid $^4$He, ultracold atomic Bose gases, charged pion and kaon condensates in rotating neutron stars, and various superconducting fermionic systems with pairing, like proton and color-superconducting components in compact stars, metallic superconductors, and neutral fermionic systems with pairing, like the neutron component in compact stars and ultracold atomic Fermi gases. Order parameters of the "mother" condensate in the superfluid and the new condensate of excitations, corresponding energy gains, critical temperatures and critical velocities are found.