Signatures of shape phase transitions in odd-mass nuclei

TL;DR

This paper investigates quantum shape phase transitions in odd-mass nuclei using a microscopic energy density functional approach, highlighting the influence of unpaired nucleons on nuclear shape changes.

Contribution

It introduces a method combining energy density functional theory with particle-plus-boson-core coupling to study shape transitions in odd-mass nuclei, with a focus on Eu and Sm isotopes.

Findings

Identification of shape phase transition signatures in odd-mass nuclei.

Demonstration of the unpaired nucleon's influence on nuclear shape evolution.

Quantitative analysis of excitation energies and transition rates across neutron numbers.

Abstract

Quantum phase transitions between competing ground-state shapes of atomic nuclei with an odd number of protons or neutrons are investigated in a microscopic framework based on nuclear energy density functional theory and the particle-plus-boson-core coupling scheme. The boson-core Hamiltonian, as well as the single-particle energies and occupation probabilities of the unpaired nucleon, are completely determined by constrained self-consistent mean-field calculations for a specific choice of the energy density functional and paring interaction, and only the strength parameters of the particle-core coupling are adjusted to reproduce selected spectroscopic properties of the odd-mass system. We apply this method to odd-A Eu and Sm isotopes with neutron number $N \approx 90$, and explore the influence of the single unpaired fermion on the occurrence of a shape phase transition. Collective wave functions of low-energy states are used to compute quantities that can be related to quantum order parameters: deformations, excitation energies, E2 transition rates and separation energies, and their evolution with the control parameter (neutron number) is analysed.