Microscopic Analysis of Nuclear Quantum Phase Transitions in the N=90 region

TL;DR

This paper investigates shape phase transitions in Nd isotopes near N=90 using relativistic energy density functionals, revealing an abrupt structural change consistent with the X(5) critical point model.

Contribution

It extends previous shape transition analyses to include triaxial deformations and provides a microscopic foundation for the observed quantum phase transition at N=90.

Findings

Reproduces experimental excitation spectra and transition probabilities.

Identifies an abrupt structural change at N=90.

Shows consistency with the X(5) critical point model.

Abstract

The analysis of shape transitions in Nd isotopes, based on the framework of relativistic energy density functionals and restricted to axially symmetric shapes in Ref. \cite{PRL99}, is extended to the region $Z = 60$, 62, 64 with $N \approx 90$, and includes both $\beta$ and $\gamma$ deformations. Collective excitation spectra and transition probabilities are calculated starting from a five-dimensional Hamiltonian for quadrupole vibrational and rotational degrees of freedom, with parameters determined by constrained self-consistent relativistic mean-field calculations for triaxial shapes. The results reproduce available data, and show that there is an abrupt change of structure at N=90 that can be approximately characterized by the X(5) analytic solution at the critical point of the first-order quantum phase transition between spherical and axially deformed shapes.