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

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.

Comments: 37 pages, 15 figures, 1 table, accepted for publication in Phys. Rev. C