Unified mechanism behind the even-parity ground state and neutron halo of 11Be* *This work was partly supported by the Strategic Priority Research Program of Chinese Academy of Sciences (XDB34000000), the National Natural Science Foundation of China (12275111) and the Fundamental Research Funds for the Central Universities (lzujbky-2021–sp41, lzujbky-2021–sp36)

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Using the axially deformed relativistic Hartree-Fock-Bogoliubov (D-RHFB) model, we explore the mechanism behind the parity inversion and halo occurrence in 11Be, which are well reproduced by the RHF Lagrangian PKA1. It is illustrated that evidently enhanced deformation effects by the π-pseudo-vector and ρ-tensor couplings in PKA1 are crucial for correctly describing both the even-parity ground state (GS) and the neutron halo of 11Be. Coupling with the deformation, the intrude component largely enhances the couplings between the even-parity orbit and the nuclear core to ensure an even-parity GS, whereas the component therein dominates the halo formation in 11Be. Moreover, the deformed halo in 11Be is found to be stabilized by the attractive inherent correlations between the and components of the halo orbit , instead of pairing correlations, which paves a new way for understanding the halo pictures in deformed unstable nuclei.