Dineutron correlations and BCS-BEC crossover in nuclear matter with the Gogny pairing force

TL;DR

This study investigates dineutron correlations and the BCS-BEC crossover in nuclear matter using the relativistic Hartree-Bogoliubov theory with Gogny pairing force, revealing the conditions under which BEC-like states may occur.

Contribution

It introduces a detailed analysis of dineutron correlations and the BCS-BEC crossover in nuclear matter using the Gogny force within a relativistic framework, providing new insights into the density regions of crossover.

Findings

Neutron pairing gaps are smaller at low densities compared to Bonn-B potential.

A true dineutron BEC state does not appear in nuclear matter.

The BCS-BEC crossover occurs within a specific density range, with the most BEC-like state near $k_{Fn} hicksim 0.3 m{fm^{-1}}$.

Abstract

The dineutron correlations and the crossover from superfluidity of neutron Cooper pairs in the $^1S_0$ pairing channel to Bose-Einstein condensation (BEC) of dineutron pairs in both symmetric and neutron matter are studied within the relativistic Hartree-Bogoliubov theory, with the effective interaction PK1 of the relativistic mean-field approach in the particle-hole channel and the finite-range Gogny force in the particle-particle channel. The influence of the pairing strength on the behaviors of dineutron correlations is investigated. It is found that the neutron pairing gaps at the Fermi surface from three adopted Gogny interactions are smaller at low densities than the one from the bare nucleon-nucleon interaction Bonn-B potential. From the normal (anomalous) density distribution functions and the density correlation function, it is confirmed that a true dineutron BEC state does not appear in nuclear matter. In the cases of the Gogny interactions, the most BEC-like state may appear when the neutron Fermi momentum $k_{Fn}\thicksim0.3 \rm{fm^{-1}}$. Moreover, based on the newly developed criterion for several characteristic quantities within the relativistic framework, the BCS-BEC crossover is supposed to realize in a revised density region with $k_{Fn}\in[0.15,0.63] \rm{fm^{-1}}$ in nuclear matter.