  A recent analysis based on the STAR measurement in relativistic heavy-ion
collision experiments provides evidence of octupole correlation in the ground
state of $^{96}$Zr, the description of which presents a challenge to nuclear
structure models. In this work, we perform projection-after-variation
calculations for $^{96}$Zr based on a multidimensionally-constrained
relativistic Hartree-Bogoliubov model. Our results show that an octupole
deformed shape is favored in energy after symmetry restoration, and this
phenomenon cannot be reproduced in the pure mean-field calculations. These
complex structures originate from the competition among various shell
structures in this mass region. Our results suggest that the allowance of
symmetry breaking at the mean-field level and the restoration of broken
symmetries are essential elements for understanding the structure of $^{96}$Zr
in density functional theories.

Nuclear Theory;Nuclear Experiment