Interplay between pairing and triaxial shape degrees of freedom in Os and Pt nuclei

Abstract

The effect of coupling between pairing and quadrupole triaxial shape vibrations on the low-energy collective states of $\gamma$-soft nuclei is investigated using a model based on the framework of nuclear energy density functionals (EDFs). Employing a constrained self-consistent mean-field (SCMF) method that uses universal EDFs and pairing interactions, potential energy surfaces of characteristic $\gamma$-soft Os and Pt nuclei with $A\approx190$ are calculated as functions of the pairing and triaxial quadrupole deformations. Collective spectroscopic properties are computed using a number-nonconserving interacting boson model (IBM) Hamiltonian, with parameters determined by mapping the SCMF energy surface onto the expectation value of the Hamiltonian in the boson condensate state. It is shown that, by simultaneously considering both the shape and pairing collective degrees of freedom, the EDF-based IBM successfully reproduces data on collective structures based on low-energy $0^{+}$ states, as well as $\gamma$-vibrational bands.