Soft modes in the proton-neutron pairing channel as precursors of deuteron condensate in N=Z nuclei

TL;DR

This paper develops a relativistic nuclear response theory within Quantum Hadrodynamics to investigate soft modes in proton-neutron pairing channels, aiming to identify precursors to deuteron condensates in N=Z nuclei.

Contribution

It introduces a parameter-free relativistic framework connecting high-energy mesons to low-energy vibrations for studying proton-neutron pairing.

Findings

Identification of soft modes as potential precursors to deuteron condensates.

Analysis of $J^{}$ and $J^{
}$ channels in $^{56}$Ni and $^{100}$Sn.

Insights into mediators of proton-neutron pairing interaction.

Abstract

Relativistic nuclear response theory is formulated for the proton-neutron pairing, or deuteron transfer, channel. The approach is based on the meson-nucleon Lagrangian of Quantum Hadrodynamics (QHD) and advances the relativistic field theory to connect consistently the high-energy scale of heavy mesons, the medium-energy range of the pion and the low-energy domain of emergent collective vibrations (phonons) in a parameter-free way. Mesons and phonons build up the in-medium nucleon-nucleon interaction in spin-isospin transfer channels, in particular, the phonon-exchange part takes care of the leading-order retardation effects. In this framework, we explore $J^{\pi} = 0^+$ and $J^{\pi} = 1^+$ channels of the nuclear response to the proton-neutron pair removal and addition in $^{56}$Ni and $^{100}$Sn with a special focus on the lowest (soft) modes as precursors of deuteron condensate and candidates for being the mediators of the proton-neutron pairing interaction.