The evolution of the pairing correlations from closed shell to midshell nuclei is analyzed in the Sn isotopes with the Finite Range Density Dependent Gogny force. As theoretical approaches we use the Hartree-Fock-Bogoliubov, the Lipkin-Nogami, their particle number projected counterparts and the full variation after particle number projection method. We find that whereas all approaches succeed ...

Symmetry-projected Hartree-Fock-Bogoliubov (HFB) equations are derived using the variational ansatz for the generalized one-body density-matrix in the Valatin form. It is shown that the projected-energy functional can be completely expressed in terms of the HFB density-matrix and the pairing-tensor. The variation of this projected-energy is shown to result in HFB equations with modified express...

Understanding the nature of Cooper pairs is essential to describe properties superconductors. The original proposal Bardeen, Cooper, and Schrieffer (BCS) was based on electrons pairing with same energy zero center-of-mass momentum. With advent new superconductors, different forms have been discussed. In particular, finite momentum received large interest. Along such finite-momentum pairs, at en...

This Letter theoretically discusses quasiparticle states and nuclear spin relaxation rates T1-1 in the quasi-one-dimensional superconductor (TMTSF)2PF6 under a magnetic field applied parallel to the conduction chains. We study the effects of Josephson-type vortices on T1(-1) by solving the Bogoliubov-de Gennes equation for p-, d- or f-wave pairing interactions. In the presence of line nodes in ...

The use of radioactive ion beams is shown to offer the possibility to study collective pairing states at high excitation energy, which are not usually accessible with stable projectiles because of large energy mismatch. In the case of two-neutron stripping reactions induced by He, we predict a population of the Giant Pairing Vibration in Pb or Sn with cross sections of the order of a millibarn,...

The magnetic flux threading a conventional superconducting ring is typically quantized in units of Φ0=hc/2e. The factor of 2 in the denominator of Φ0 originates from the existence of two different types of pairing states with minima of the free energy at even and odd multiples of Φ0. Here we show that spatially modulated pairing states exist with energy minima at fractional flux values, in part...

We study the pairing Hamiltonian in a set of non degenerate levels. First, we discuss the spontaneous breaking of the U (1) symmetry in the path integral framework in the degenerate situation. Next, in the multilevel case, we obtain approximate, but accurate, expressions for the ground state energy in terms of a few moments of the single particle levels distribution when the system is in a supe...