SYNCHRONIZATION PROPERTIES OF A STRONGLY COUPLED SQUID CELL WITHIN THE WERTHAMER MODEL

The synchronization properties of two Josephson junctions in a strongl y coupled SQUID cell are studied. within the Werthamer model. The gene ral behavior is found to be similarly to that of the RCSJ model. Howev er, there are quantitative differences, e.g. an enhanced phase shift b etween the voltage oscillations in an autonomous SQUID cell and change s of the synchronization regions (Shapiro steps) in the current-voltag e characteristic of a microwave-driven SQUID. They both can be attribu ted to the highly nonlinear shape of the (smeared) BCS current amplitu des used within the Werthamer theory.