Reflection symmetry instability at high spins in 162,164Yb

TL;DR

This study investigates shape changes and symmetry instabilities at high spins in 162Yb and 164Yb nuclei, revealing the emergence of nonaxial octupole deformations and their underlying dynamics using advanced nuclear models.

Contribution

It provides new insights into high-spin shape evolution and octupole correlations in ytterbium isotopes through self-consistent and microscopic modeling.

Findings

Nonaxial octupole deformations appear in 162Yb at high spins.

Nonaxial quadrupole shapes dominate in 164Yb at fast rotation.

Disappearance of octupole vibrational modes leads to symmetry breaking.

Abstract

A shape evolution of 162,164Yb in yrast states is traced using the self-consistent Skyrme Hartree-Fock calculations. We found that nonaxial octupole deformations (in particular, Y_{31} term) become favorable at large rotational frequencies (> 0.4 MeV) in 162Yb, while in 164Yb a nonaxial quadrupole shape is dominant at fast rotation. The cranked Nilsson model and random phase approximation are used to understand the dynamics of octupole correlations in both nuclei. We demonstrate that the disappearance of one of the octupole vibrational modes in the rotating frame gives rise to the nonaxial octupole deformations in 162Yb, while the octupole modes are nonzero in 164Yb.