  We report the first beyond-mean-field study of low-lying parity-doublet
states in 224Ra by extending the multireference relativistic energy density
functional method to include dynamical correlations related to symmetry
restoration and quadrupole-octupole shape fluctuation with a generator
coordinate method combined with parity, particle-number, and angular-momentum
projections. We clarify full microscopically that the origin of spin-dependent
parity splitting in low-spin states is related to the octupole shape
stabilization of positive-parity states, the dominated shapes of which drift
gradually to that of negative-parity ones.
