Spin-triplet pairing in large nuclei

TL;DR

This paper investigates the transition from spin-singlet to spin-triplet pairing in very large nuclei using Hartree-Fock-Bogoliubov equations, confirming that large nuclei favor triplet pairing depending on orbital configurations.

Contribution

It provides the first detailed theoretical analysis of spin-triplet pairing in large nuclei, identifying conditions and specific mass regions where this phase is favored.

Findings

Large nuclei (A ~ 130-140) favor spin-triplet pairing.

The transition depends on the orbitals at the Fermi energy.

Triplet pairing becomes dominant in extremely large nuclei.

Abstract

The nuclear pairing condensate is expected to change character from spin-singlet to spin-triplet when the nucleus is very large and the neutron and proton numbers $Z,N$ are equal. We investigate the transition between these two phases within the framework of the Hartree-Fock-Bogoliubov equations, using a zero-range interaction to generate the pairing. We confirm that extremely large nucleus would indeed favor triplet pairing condensates, with the Hamiltonian parameters taken from known systematics. The favored phase is found to depend on the specific orbitals at the Fermi energy. The smallest nuclei with a well-developed spin-triplet condensate are in the mass region A ~ 130-140.