Configuration interaction in symmetry-conserving covariant density functional theory

A new method to calculate spectroscopic properties of deformed nuclei is proposed: configuration interaction on top of projected density functional theory (CI-PDFT). The general concept of this approach is discussed in the framework of covariant density functional theory and its validity is illustrated in an application to the yrast band of the nucleus ${}^{54}\mathrm{Cr}$. It is found that the experimentally observed excitation energies for the yrast band in ${}^{54}\mathrm{Cr}$ can be well reproduced. In contrast to conventional shell-model calculations, there is no core and only a relatively small number of configurations is sufficient for a satisfying description. No new parameters are necessary, because the effective interaction is derived from an universal density functional given in the literature.

Figure 1

The neutron (left panel) and proton (right panel) single-particle levels for ${}^{54}\mathrm{Cr}$, as functions of the quadrupole deformation ${\beta }_2$. The dashed and solid lines represent the levels with negative and positive parities, respectively. The thick lines with open circles denote the position of the Fermi energy.

Figure 2

Theoretical yrast band (solid circles) and the angular momentum projected states for some important configurations which are explained in Table 1 in ${}^{54}\mathrm{Cr}$. Inset: Angular momentum projected states for all the configurations considered together with the yrast band (solid circles). Note that the energy of the yrast state $0^{+}$ is renormalized to zero.

Figure 3

Comparison between the calculated energy levels (MeV) and $B(E2;\downarrow )$ transition probabilities $\left(e^2{\mathrm{fm}}^4\right)$ and the corresponding data available in Refs. [56, 60] for the yrast band with the angular momentum $I\le 10$, and also the nonyrast $I=2,4$ states.