Josephson effect in S FXS F junctions
N. M. Chtchelkatchev, W. Belzig*, C. Bruder*
L. D. Landau Institute for Theoretical Physics RAS, 117940 Moscow, Russia
*Departement Physik und Astronomie, Universität Basel, 4056 Basel, Switzerland
PACS: 74.50.+r, 74.80.-g, 75.70.-i
Abstract
We investigate the Josephson effect in S FXS F junctions, where S F is a superconducting material with a
ferromagnetic exchange field, and X a weak link. The critical current
Ic increases with the (antiparallel) exchange fields if the
distribution of transmission eigenvalues of the X-layer has its
maximum weight at small values. This exchange field enhancement of the
supercurrent does not exist if X is a diffusive normal metal. At low
temperatures, there is a correspondence between the critical current
in an S FIS F junction with collinear orientations of
the two exchange fields, and the AC supercurrent amplitude in an SIS
tunnel junction. The difference of the exchange
fields h1-h2 in an S FIS F junction corresponds to
the potential difference V1-V2 in an SIS junction; i.e., the
singularity in Ic [in an S FIS F junction] at
|h1-h2|=Δ1+Δ2 is the analogue of the Riedel peak.
We also discuss the AC Josephson effect in S FIS F
junctions.