Quenching of pairing correlations – a simple model for rotating nuclei

Adding a Kelvin momentum constraint to the Routhian HF equations one generates intrinsic vortical currents in the HF solution and it is found that one may simply reproduce in such a way the HFB dynamical properties of rotating nuclei. From the analogy between magnetic and rotating systems, one derives a model for the quenching of pairing correlations with rotation, introducing a critical angular velocity (Ω_c) – analogous to the critical field in supraconductors – above which pairing vanishes. An important feature of this model is the existence of an universal dependence between the angular velocity Ω and the intrinsic angular velocity ω, where Ω_c is playing an important role. Taking stock of this model, it is then shown that this dependence could be modelised by a simple two parameter formula, both parameters being completely determined from properties of the band-head (zero-spin) HFB solution. From calculation in five nuclei, the validity of this modelised Routhian approach is assessed. It is clearly shown to be very good in cases where the evolution of rotational properties is only governed by the coupling between the global rotation and the pairing-induced intrinsic vortical currents. It therefore provides a sound ground base for evaluating the importance of coupling of rotation with other modes (shape distortions, quasiparticle degrees of freedom).