BCS-BEC Crossover and Thermodynamics in Asymmetric Nuclear Matter with Pairings in Isospin I=0 and I=1 Channels

TL;DR

This paper explores the BCS-BEC crossover in asymmetric nuclear matter, revealing how neutron-proton pairs can form a BEC at low densities and how including I=1 pairing alters the phase diagram and superfluid properties.

Contribution

It introduces a mean field analysis of the phase diagram considering both I=0 and I=1 pairings, highlighting new phases and the suppression of gapless states.

Findings

Neutron-proton pairs can form BEC at low density.

Including I=1 pairing significantly alters the phase structure.

All excited nucleons become fully gapped in the new phase.

Abstract

The BCS-BEC crossover and phase diagram for asymmetric nuclear superfluid with pairings in isospin I = 0 and I = 1 channels are investigated at mean field level, by using a density dependent nucleon-nucleon potential. Induced by the in-medium nucleon mass and density dependent coupling constants, neutron-proton Cooper pairs could be in BEC state at sufficiently low density, but there is no chance for the BEC formation of neutron-neutron and proton-proton pairs at any density and asymmetry. We calculate the phase diagram in asymmetry-temperature plane for weakly interacting nuclear superfluid, and find that including the I = 1 channel changes significantly the phase structure at low temperature. There appears a new phase with both I = 0 and I = 1 pairings at low temperature and low asymmetry, and the gapless state in any phase with I = 1 pairing is washed out and all excited nucleons are fully gapped.