The pairing interaction induces particle-particle correlations that are essential in defining the properties of finite quantum many body systems in their ground and neighbouring states. The two-nucleon transfer reactions turned to be a very specific probe of this pairing.
The experimental transfer probabilities for one- and two-neutron transfer channels as a function of the distance of closest approach have been extracted for the closed shell 40Ca+96Zr, superfluid 60Ni+116Sn and heavy 118Sn+206Pb systems, from the Coulomb barrier energy to energies corresponding to large distances of closest approach. For the superfluid 60Ni+116Sn system, the experimental two-neutron transfer probabilities were reproduced by incorporating neutron-neutron correlations (D. Montanari et al., Phys. Rev. Lett. 113 (2014) 052501).
Very recently, this study has been characterized as the nuclear analogue
to the (alternating-current) Josephson effect (G. Potel, F. Barranco, E. Vigezzi, and R. A. Broglia, Phys. ReV. C 103 (2020) L021601).
The talk will focus on the main outcome of these recent studies, critically addressing the new achievements, the present problems and new challenges.