Pair-vibrational states in the presence of neutron-proton pairing

TL;DR

This paper investigates pair-vibrational states in a system with neutron-neutron, proton-proton, and neutron-proton pairing, revealing complex spectra and the impact of pairing interactions, using the variational configuration interaction method.

Contribution

It introduces the use of the variational configuration interaction method to accurately analyze pair vibrations with neutron-proton pairing, showing good agreement with exact solutions.

Findings

Rich spectrum of low-lying excited states

Large impact of pairing matrix element ratios on spectra

VCI method matches exact solutions for large degeneracies

Abstract

Pair vibrations are studied for a Hamiltonian with neutron-neutron, proton-proton and neutron-proton pairing. The spectrum is found to be rich in strongly correlated, low-lying excited states. Changing theratio of diagonal to off-diagonal pairing matrix elements is found to have a large impact on the excited-state spectrum. The variational configuration interaction (VCI) method, used to calculate the excitation spectrum, is found to be in very good agreement with exact solutions for systems with large degeneracies having equal T=0 and T=1 pairing strengths.