@article{
  author = {Luo, Miss Yu-Xuan; Liu, Dr. Quan;  Pan, Mr. Xue-An; Chang, Mr. Xiao; Guo, Prof. Jianyou 郭建友; },
  title = {Deformed neutron halos with shape decoupling in neutron-rich magnesium isotopes},
  keywords = {exotic nuclei;resonant state;deformed halo;the complex momentum representation method;complex momentum representation method;},
  abstract = {Background: The exploration of neutron-rich nuclei far from stability has revealed exotic phenomena like the  change of magic numbers, shape coexistence, and halo formation. Neutron-rich magnesium isotopes provide a  pivotal testing ground for understanding how shell evolution, deformation, and continuum coupling collectively  govern nuclear structure near the drip line.  Purpose: This work aims to systematically investigate the ground-state properties and the emergence of deformed  neutron halos in even-even magnesium isotopes34−44Mg, with a focus on the microscopic mechanisms driving  shell closure quenching, deformation development, and halo formation.  Methods: We employ the deformed relativistic mean-field theory combined with the complex momentum representation and BCS pairing (DRMF-CMR-BCS). This framework self-consistently treats deformation, pairing correlations, and continuum coupling, providing a unified description of bound, resonant, and continuum states. Calculations are performed using the NL3 effective interaction.  Results: Our calculations reveal the microscopic mechanism for the collapse of the N = 20 and N = 28 shell  closures, identifying it as a cooperation of monopole drift in key neutron orbitals (e.g., 1/2−1, 3/2−2) and the stabilization of prolate deformation. In 40,42,44Mg, we predict the universal emergence of deformed halos characterized by a striking shape decoupling: a prolate core coexists with an oblate halo. This halo is predominantly formed by low-angular-momentum orbitals, with the dominant contributor shifting from a narrow resonant state (3/2−2) in 40Mg to a weakly bound orbital (3/2−2) in 42Mg. The anomalous occupancy of narrow resonances underscores the important role of pairing, enhanced continuum coupling.  Conclusions: The structure of neutron-rich Mg isotopes is governed by the intricate competition between single-particle energies, deformation, pairing, and the continuum. Our calculations offer clear, testable predictions for future rare-isotope beam experiments.},
  doi = {10.12074/202604.00293},
  url = {https://chinaxiv.org/abs/202604.00293},
  timestamp = {2026-04-30},
}