Dineutron formation and breaking in $^8$He

TL;DR

This paper investigates dineutron correlations in $^8$He, comparing ground and excited states, and suggests weaker dineutron pairing in the ground state with potential condensation in an excited state, emphasizing core attraction's role.

Contribution

It introduces a novel framework to describe dineutron correlations and explores their formation mechanism in neutron-rich nuclei, specifically in $^8$He.

Findings

Dineutron correlation is weaker in $^8$He ground state than in $^6$He.

Possibility of dineutron condensation in an excited $0^+$ state of $^8$He.

Core attraction is crucial for dineutron condensation formation.

Abstract

We discuss the correlation of the spin-singlet two-neutron pair, the dineutron correlation, in the ground and excited $0^+$ states of $^8$He by using a method to describe the dineutron correlation in neutron-rich nuclei, the dineutron condensate wave function. The shell-model configuration and the dineutron configuration compete with each other in the ground state of $^8$He. We compare the ground state structure of $^8$He with that of $^6$He and suggest that the dineutron correlation is weaker in the ground state of $^8$He than $^6$He. We also suggest the possibility of the dineutron condensation in an excited $0^+$ state of $^8$He. In addition, we investigate the formation mechanism of the dineutron condensation in $^8$He by using a newly developed framework, $\alpha$ and dineutron condensate wave function, and conclude that the attraction from the core is essential for the formation of the dineutron condensation.