Impact of pairing correlations on the orientation of the nuclear spin

For the first time, the tilted axis cranking covariant density functional theory with pairing correlations has been formulated and implemented in a fully self-consistent and microscopic way to investigate the evolution of the spin axis and the pairing effects in rotating triaxial nuclei. The measured energy spectrum and transition probabilities for the ${}^{135}\mathrm{Nd}$ yrast band are reproduced well without any ad hoc renormalization factors when pairing effects are taken into account. A transition from collective to chiral rotation has been demonstrated. It is found that pairing correlations introduce additional admixtures in the single-particle orbitals, and, thus, influence the structure of tilted axis rotating nuclei by reducing the magnitude of the proton and neutron angular momenta while merging their direction.

Figure 1

Total Routhians for the 1-qp and 3-qp configurations as functions of the tilt angle $\theta$ at the rotational frequencies $\hslash \omega =0.2$ (top), 0.3 (center), 0.4 (bottom) MeV. The circles and triangles represent the local minimum points for the 1-qp and 3-qp configurations, respectively.

Figure 2

Rotational energy (upper panel) and rotational frequency (lower panel) as functions of the angular momentum in comparison with the data of Ref. [15] (solid dots). Here, the excitation energies are the relative energy differences with respect to the ground state.

Figure 3

Neutron ${\mathit{J}}_{\nu }$ and proton ${\mathit{J}}_{\pi }$ angular momentum vectors for both the 1-qp (left) and 3-qp (right) bands. Different types of arrows denote the results at different rotational frequencies. Note that ${\mathit{J}}_{\pi }$ for the 1-qp band is negligible at $\hslash \omega =0.1$ MeV.

Figure 4

Angular momentum alignments for the 1-qp and 3-qp configurations on the $z$ axis (upper panels) and $x$ axis (lower panels) of the neutron holes in the $h_{11/2}$ shell (left) and the $\left(g_{7/2}{d}_{5/2}{d}_{3/2}{s}_{1/2}\right)$ shell (right).

Figure 5

Calculated $B\left(M1\right)$ (upper panel) and $B\left(E2\right)$ (lower panel) values as functions of the angular momentum in comparison with data [10] (solid dots).