Covariant density functional theory: Reexamining the structure of superheavy nuclei

TL;DR

This study systematically examines superheavy nuclei using covariant density functional theory with various models, assessing their predictions on structure, shell gaps, and decay properties, and finds limited impact of the N=172 shell gap contrary to previous studies.

Contribution

It provides a comprehensive comparison of covariant energy density functionals for superheavy nuclei, highlighting differences in predicted shell effects and shapes, and challenges previous assumptions about the N=172 shell gap.

Findings

Limited impact of N=172 shell gap on superheavy nuclei structure.

Some functionals predict a significant N=184 shell gap.

Experimental data do not discriminate between different model predictions.

Abstract

A systematic investigation of even-even superheavy elements in the region of proton numbers $100 \leq Z \leq 130$ and in the region of neutron numbers from the proton-drip line up to neutron number $N=196$ is presented. For this study we use five most up-to-date covariant energy density functionals of different types, with a non-linear meson coupling, with density dependent meson couplings, and with density-dependent zero-range interactions. Pairing correlations are treated within relativistic Hartree-Bogoliubov (RHB) theory based on an effective separable particle-particle interaction of finite range and deformation effects are taken into account. This allows us to assess the spread of theoretical predictions within the present covariant models for the binding energies, deformation parameters, shell structures and $\alpha$-decay half-lives. Contrary to the previous studies in covariant density functional theory, it was found that the impact of $N=172$ spherical shell gap on the structure of superheavy elements is very limited. Similar to non-relativistic functionals some covariant functionals predict the important role played by the spherical $N=184$ gap. For these functionals (NL3*, DD-ME2 and PC-PK1), there is a band of spherical nuclei along and near the $Z=120$ and $N=184$ lines. However, for other functionals (DD-PC1 and DD-ME$\delta$) oblate shapes dominate at and in the vicinity of these lines. Available experimental data are in general described with comparable accuracy and do not allow to discriminate these predictions.