We investigate the Josephson coupling between two superconductors mediated through an infinite U Anderson impurity, adapting a variational wave-function approach which has proved successful for the Kondo model. Unlike the Kondo problem, however, a crossing of singlet and doublet state energies may be produced by varying the ratio of Kondo energy to superconducting gap, in agreement with recent work of Clerk and Ambegaokar. We construct the phase diagram for the junction and discuss properties of different phases. In addition, we find the singlet and doublet state energies within a slave-boson mean-field approach. We find the slave-boson mean-field treatment is unable to account for the level crossing.
|Number of pages||5|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - 1 Sep 2000|