$\alpha$-like quartetting in the excited states of proton-neutron pairing Hamiltonians

TL;DR

This paper extends the quartet condensation model to excited states in proton-neutron pairing systems, demonstrating accurate descriptions by breaking and replacing quartets, analogous to pair-breaking in like-particle pairing.

Contribution

It introduces a novel approach to describe excited states in proton-neutron pairing Hamiltonians by breaking quartets, expanding the quartet condensation framework.

Findings

Accurately describes low-lying excited states using quartet breaking

Demonstrates the method's effectiveness for isovector and isovector-isoscalar pairing

Provides a new analogy to pair-breaking in nuclear models

Abstract

Previous studies have shown that the ground state of systems of nucleons composed by an equal number of protons and neutrons interacting via proton-neutron pairing forces can be described accurately by a condensate of $\alpha$-like quartets. Here we extend these studies to the low-lowing excited states of these systems and show that these states can be accurately described by breaking a quartet from the ground state condensate and replacing it with an "excited" quartet. This approach, which is analogous to the one-broken-pair approximation employed for like-particle pairing, is analysed for various isovector and isovector-isoscalar pairing