Proton-neutron pairing and alpha-like quartet correlations in atomic nuclei

Description
ABSTRACT:
Recently it has been shown that proton-neutron pairing in N=Z nuclei
can be accurately described by a condensate of alpha-like quartets built by two neutrons and two protons coupled to the total isospin T=0 [1].
Contrary to the common believe, proton-neutron pairing and alpha-like quartet correlations are important not only for self-conjugate nuclei but also for nuclei away of  N=Z line.
In the latter case the condensate of alpha-like quartets coexists with the condensate of nucleons in excess relative to the isotope with N=Z [2].
The comparison with the exact solvable models show that the ansatz of the quartet condensation is able to describe with high precision the pairing correlations in nuclei with protons and neutrons in the same major shell.
As an application we shall discuss the contribution of proton-neutron pairing to the Wigner energy, which appears to be much more significant than the predictions of BCS-type models.
1. N. Sandulescu, D. Negrea, J. Dukelsky, C. W. Johnson, Phys. Rev. C86, 041302 (R)
2. N. Sandulescu, D. Negrea, C. W. Johnson, Phys. Rev. C Phys. Rev. C85, 061303 (R)