Multireference covariant density functional theory for shape coexistence and isomerism in 43S

摘要: We present a new development in the multireference covariant density functional theory (MR-CDFT) for the low-lying states of odd-mass nuclei by mixing the configurations not only with different intrinsic quadrupole shapes, but also with different $K$ quantum numbers. All the configurations are projected onto good particle numbers and angular momenta. The success of this newly developed framework is illustrated in the application to the low-lying states of $^{43}$S near the neutron magic number $N=28$ with shape coexistence. Our results indicate that the ground state, $3/2^-_1$, is predominantly composed of the intruder prolate one-quasiparticle (1qp) configuration $\nu1/2^-[321]$. In contrast, the $7/2^-_1$ state is identified as a high-$K$ isomer, primarily built on the prolate 1qp configuration $\nu7/2^-[303]$. Additionally, the $3/2^-_2$ state is found to be an admixture dominated by an oblate configuration with $K^\pi = 1/2^-$, along with a small contribution from a prolate configuration with $K^\pi = 3/2^-$. These results demonstrate the capability of MR-CDFT to capture the intricate interplay among shape coexistence, configuration mixing, and isomerism in the low-energy structure of odd-mass nuclei around $N = 28$, without invoking triaxiality.