Shell-model-like approach based on cranking covariant density functional theory: Band crossing and shape evolution in 60Fe

The shell-model-like approach is implemented to treat the cranking many-body Hamiltonian based on the covariant density functional theory including pairing correlations with exact particle number conservation. The self-consistency is achieved by iterating the single-particle occupation probabilities back to the densities and currents. As an example, the rotational structures observed in the neutron-rich nucleus Fe-60 are investigated and analyzed. Without introducing any ad hoc parameters, the bandheads, the rotational spectra, and the relations between the angular momentum and rotational frequency for the positive-parity band A and negative-parity bands B and C are well reproduced. The essential role of the pairing correlations is revealed. It is found that for band A, the band crossing is due to the change of the last two occupied neutrons from the 1f(5/2) signature partners to the 1g(9/2) signature partners. For the two negative-parity signature partner bands B and C, the band crossings are due to the pseudocrossing between the 1f(7/2,5/2) and the 1f(5/2,1/2) orbitals. Generally speaking, the deformation parameters beta for bands A, B, and C decrease with rotational frequency. For band A, the deformation jumps from beta approximate to 0.19 to beta approximate to 0.29 around the band crossing. In comparison with its signature partner band C, band B exhibits appreciable triaxial deformation.