Coupling of pairing and triaxial shape vibrations in collective states of $\gamma$-soft nuclei

TL;DR

This paper explores the coupling of shape and pairing vibrations in gamma-soft nuclei using self-consistent mean-field and interacting boson approximation methods, highlighting the importance of dynamical pairing in nuclear structure.

Contribution

It introduces a boson-number non-conserving Hamiltonian to explicitly include pairing vibrations in the modeling of collective nuclear states.

Findings

Dynamical pairing significantly affects low-energy spectra.

Coupling influences structures built on low-energy 0+ states.

Results demonstrate the importance of pairing in gamma-soft nuclei.

Abstract

In addition to shape oscillations, low-energy excitation spectra of deformed nuclei are also influenced by pairing vibrations. The simultaneous description of these collective modes and their coupling has been a long-standing problem in nuclear structure theory. Here we address the problem in terms of self-consistent mean-field calculations of collective deformation energy surfaces, and the framework of the interacting boson approximation. In addition to quadrupole shape vibrations and rotations, the explicit coupling to pairing vibrations is taken into account by a boson-number non-conserving Hamiltonian, specified by a choice of a universal density functional and pairing interaction. An illustrative calculation for $^{128}$Xe and $^{130}$Xe shows the importance of dynamical pairing degrees of freedom, especially for structures built on low-energy $0^+$ excited states, in $\gamma$-soft and triaxial nuclei.