The evolution of the chiral symmetry in cesium isotopes

TL;DR

This study investigates the evolution of chiral symmetry in cesium isotopes using a microscopic three-dimensional tilted axis cranking covariant density functional theory, revealing the transition from planar to chiral rotation and its dependence on neutron number.

Contribution

It provides a detailed microscopic analysis of chiral symmetry evolution in cesium isotopes, identifying the transition points and explaining the neutron number dependence of chiral rotation.

Findings

Transition from planar to chiral rotation in $^{121-133}$Cs.

Critical rotational frequency decreases with increasing neutron number.

Good agreement with experimental energy spectra and transition ratios.

Abstract

Following the reports of candidate chiral doublet bands observed in cesium isotopes, the possible chiral candidates and the evolution of three-dimensional rotation in $^{120-134}{\textrm{Cs}}$ are investigated within the microscopic three-dimensional tilted axis cranking covariant density functional theory (3DTAC-CDFT). By investigating the evolution of the polar angle $\theta$ and azimuth angle $\varphi$ as a function of rotational frequency $\hbar\omega$, the transition from the planar rotation to the chiral rotation has been found in $^{121-133}{\textrm{Cs}}$. The corresponding critical rotational frequency $\omega_{\textrm{crit}}$ of the appearance of chiral aplanar rotation decreases as neutron number increases, which can be attributed to the neutrons in $(gd)$ and $(sd)$ shells having smaller angular momentum components along both the short and long axes, and larger components along medium axis, respectively. In comparison, only planar rotation has been obtained in $^{120,134}{\textrm{Cs}}$. With these interpretations, the obtained $I\sim\hbar\omega$ and energy spectra as well as $B(M1)/B(E2)$ values show reasonable agreement with the available experimental data. In addition, the evolution of quadrupole deformation $\beta$ and triaxial deformation $\gamma$ are also discussed.