Mixed-Spin Pairing Condensates in Heavy Nuclei

TL;DR

This paper demonstrates that heavy nuclei with neutron-proton imbalance can support mixed-spin pairing condensates, revealing a new pairing mode that influences nuclear energy surfaces and low-lying excitations.

Contribution

It introduces the concept of mixed-spin pairing condensates in heavy nuclei and predicts their occurrence in neutron-proton imbalanced systems using the Bogoliubov-de Gennes framework.

Findings

Mixed-spin condensates occur with isospin imbalance.

Energy surfaces are soft, indicating low-lying excitations.

Such condensates are absent in equal neutron-proton systems.

Abstract

We show that the Bogoliubov-de Gennes equations for nuclear ground-state wave functions support solutions in which the condensate has a mixture of spin-singlet and spin-triplet pairing. We find that such mixed-spin condensates do not occur when there are equal numbers of neutrons and protons, but only when there is an isospin imbalance. Using a phenomenological Hamiltonian, we predict that such nuclei may occur in the physical region within the proton dripline. We also solve the Bogoliubov-de Gennes equations with variable constraints on the spin-singlet and spin-triplet pairing amplitudes. For nuclei that exhibit this new pairing behavior, the resulting energy surface can be rather soft, suggesting that there may be low-lying excitations associated with the spin mixing.