Proton-neutron pairing vibrations in N=Z nuclei: Precursory soft mode of isoscalar pairing condensation

TL;DR

This paper investigates proton-neutron pairing vibrations in N=Z nuclei, revealing a potential precursor to isoscalar pairing condensation through enhanced collectivity in specific nuclear states.

Contribution

It demonstrates the emergence of a T=0 pn-pairing vibrational mode as a precursor to pairing condensation using a novel RPA approach with Skyrme functional.

Findings

Increased collectivity of the 1+ state with stronger T=0 pairing

Identification of a soft mode indicating proximity to pairing condensation

Potential critical phenomenon in N=Z nuclei

Abstract

L=0 proton-neutron ($pn$) pair-addition and pair-removal strengths in $^{40}$Ca and $^{56}$Ni are investigated by means of the $pn$ particle-particle random-phase approximation employing a Skyrme energy-density functional. It is found that the collectivity of the lowest $J^\pi = 1^+$ state in the adjacent odd-odd nuclei becomes stronger as the strength of the isoscalar (T=0) pairing interaction increases. The results suggest the emergence of the T=0 $pn$-pairing vibrational mode as a possible critical phenomenon toward the T=0 pairing condensation.