Tunneling through an Anderson impurity between superconductors
Abstract
We consider an Anderson impurity (A) weakly connected to a superconducting electrode (S) on one side and a superconducting or a normalmetal electrode (N) on the other side. A general pathintegral formalism is developed and the response of SAN and SAS junctions to a constant voltage bias V is elucidated, using a combination of the Keldysh technique (to handle nonequilibrium effects) and a dynamical meanfield approximation (to handle repulsive Hubbard interactions). An interesting physics is exposed at subgap voltages (eV<Δ for SAN and eV<2Δ for SAS). For an SAN junction, Andreev reflection is strongly affected by Coulomb interaction. For superconductors with pwave symmetry the junction conductance exhibits a remarkable peak at eV<Δ, while for superconductors with swave symmetric pair potential the peak is shifted towards the gap edge eV=Δ and strongly suppressed if the Hubbard repulsive interaction increases. Electron transport in SAS junctions is determined by an interplay between multiple Andreev reflection (MAR) and Coulomb effects. For swave superconductors the usual peaks in the conductance that originate from MAR are shifted by interaction to larger values of V. They are also suppressed as the Hubbard interaction strength grows. For pwave superconductors the subgap current is much larger and the IV characteristics reveal an interesting feature, namely, a peak in the current resulting from a midgap bound state in the junction.
 Publication:

Physical Review B
 Pub Date:
 April 2001
 DOI:
 10.1103/PhysRevB.63.134515
 arXiv:
 arXiv:condmat/0007098
 Bibcode:
 2001PhRvB..63m4515A
 Keywords:

 74.40.+k;
 72.10.d;
 74.20.z;
 74.50.+r;
 Fluctuations;
 Theory of electronic transport;
 scattering mechanisms;
 Theories and models of superconducting state;
 Tunneling phenomena;
 point contacts weak links Josephson effects;
 Condensed Matter  Strongly Correlated Electrons;
 Condensed Matter  Superconductivity
 EPrint:
 14 twocolumn pages including 5 eps figures