Reentrance phenomenon of superfluid pairing in hot rotating nuclei

Reentrance phenomenon of superfluid pairing in highly rotating excited (hot) nuclei is studied within the Bardeen-Cooper-Schrieffer (BCS)-based approach (the FTBCS1), taking into account the effect of quasiparticle number fluctuations (QNF) on the pairing field at finite temperature and angular momentum within the pairing model plus noncollective rotation along the symmetry axis. The numerical calculations are carried out for the pairing gaps and level densities in 104Pd, of which an anomalous enhancement of level density at low excitation energy E* and high angular momentum J has been experimentally observed. The results obtained show that the QNF within the FTBCS1 theory smooth out the superfluid-normal phase transition and lead to the appearance of pairing reentrance phenomenon in hot rotating nuclei. This feature can be clearly seen in the behavior of pairing gap obtained at low E* and high J. The good agreement between the level densities obtained within the FTBCS1 and those extracted from the experiment indicates that the observed enhancement in the level densities of 104Pd nucleus is a manifestation of the pairing reentrance phenomenon.