New magicity $N=32$ and $34$ triggered by strong couplings between Dirac inversion partners

TL;DR

This paper investigates the emergence of new magic numbers in calcium isotopes, attributing it to strong couplings between specific Dirac inversion partner orbits, and predicts where these magicities persist or vanish.

Contribution

It introduces a novel mechanism involving Dirac inversion partners to explain and predict new magic numbers in neutron-rich isotopes.

Findings

Strong couplings between Dirac inversion partners are key to new magic numbers.

Magicity at N=32 persists until 48S but vanishes in 46Si.

The mechanism explains recent experimental observations.

Abstract

Inspired by recent experiments, the successive new magicity $N = 32$ and $34$ in Ca isotopes are studied within the relativistic density functional theory. It is illustrated that the strong couplings between the $s_{1/2}$ and neutron ($\nu$) $\nu2p_{1/2}$ orbits, here referred as "Dirac inversion partners" (DIPs), play a key role in opening both subshells $N = 32$ and $34$. Such strong couplings originate from the inversion similarity between the DIPs, that the upper component of the Dirac spinor of one partner shares the same orbital angular momentum as the lower component of the other, and vice versa. Following the revealed mechanism, it is predicted that the magicity $N = 32$ is reserved until $^{48}$S, but vanishes in $^{46}$Si.