Unified BCS-like model of pairing and alpha-correlations

TL;DR

This paper develops a unified BCS-like model that incorporates both nucleonic pairing and alpha-type correlations, revealing two mutually exclusive condensate phases and a phase transition driven by neutron excess.

Contribution

It introduces a combined variational wave function for nucleonic and alpha correlations, deriving gap equations and analyzing phase transitions in nuclear matter.

Findings

Two distinct condensate phases that cannot coexist.

Alpha condensate dominates at N=Z, transitioning to nucleon condensates with neutron excess.

First order phase transition driven by neutron excess.

Abstract

We construct a BCS-like model that combines nucleonic pairing correlations and possible quartic correlations of alpha-type in a single variational wave function and derive corresponding gap equations. In the approximation of large logarithms typical for the BCS approach, we show that the system reveals two possible types of a condensate which cannot coexist. If the alpha-type condensate prevails at N=Z, the growth of the neutron excess will naturally lead to the first order phase transition to the nucleon condensates.