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Halos epitomize the fascinating interplay between weak binding, shell evolution, and deformation effects, especially in nuclei near the drip line. In this Letter, we apply the state-of-the-art ab initio valence-space in-medium similarity renormalization group approach to predict potential candidates for one- and two-neutron halo in the intermediate-mass region. Notably, we use spectroscopic factors (SF) and two-nucleon amplitudes (TNA) as criteria for suggesting one- and two-neutron halo candidates, respectively. This approach is not only theoretically sound but also amenable to experimental validation. Our research focuses on Mg, Al, Si, P, and S neutron-drip-line nuclei, offering systematic predictions of neutron halo candidates in terms of separation energies, SF (TNA), and average occupation. The calculation suggests the ground states of ^40, 42, 44, 46Al, ^41, 43, 45, 47Si, ^46, 48P, and ^47, 49S are promising candidates for one-neutron halos, while ^40, 42, 44, 46Mg, ^45, 47Al, ^46, 48Si, ^49P, and ^50S may harbor two-neutron halos. In addition, the relative mean-square neutron radius between halo nuclei and inner core is calculated for suggested potential neutron halos. Finally, the relations of halo formations and shell evolution are discussed.
Li et al. (Wed,) studied this question.