Pairing vibrations in the interacting boson model based on density functional theory

TL;DR

This paper introduces a novel method integrating shape and pairing vibrations into the interacting boson model using density functional theory, improving the accuracy of nuclear excitation energy predictions.

Contribution

It develops a boson-number non-conserving IBM Hamiltonian derived from self-consistent mean-field calculations to incorporate pairing vibrations.

Findings

Lowered energies of excited 0+ state bands.

Quantitative agreement with experimental spectroscopic data.

Consistent results with the collective Hamiltonian approach.

Abstract

We propose a method to incorporate the coupling between shape and pairing collective degrees of freedom in the framework of the interacting boson model (IBM), based on the nuclear density functional theory. To account for pairing vibrations, a boson-number non-conserving IBM Hamiltonian is introduced. The Hamiltonian is constructed by using solutions of self-consistent mean-field calculations based on a universal energy density functional and pairing force, with constraints on the axially-symmetric quadrupole and pairing intrinsic deformations. By mapping the resulting quadrupole-pairing potential energy surface onto the expectation value of the bosonic Hamiltonian in the boson condensate state, the strength parameters of the boson Hamiltonian are determined. An illustrative calculation is performed for $^{122}$Xe, and the method is further explored in a more systematic study of rare-earth $N=92$ isotones. The inclusion of the dynamical pairing degree of freedom significantly lowers the energies of bands based on excited $0^+$ states. The results are in quantitative agreement with spectroscopic data, and are consistent with those obtained using the collective Hamiltonian approach.