BCS-BEC crossover and thermodynamics in asymmetric nuclear matter with pairings in isospinI=0andI=1channels

Abstract

The Bardeen/Cooper/Schrieffer--Bose-Einstein condensation (BCS-BEC) crossover and phase diagram for asymmetric nuclear superfluid with pairings in isospin $I=0$ and $I=1$ channels are investigated at the 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.