Interplay between Static and Dynamic Properties of Semifluxons in YBa2Cu3O7-delta 0-pi Josephson Junctions

We have investigated the static and dynamic properties of long YBa2Cu3O7 0- Josephson junctions and compared them with those of conventional 0 junctions. Scanning SQUID microscope imaging has revealed the presence of a semifluxon at the phase discontinuity point in 0- Josephson junctions. Zero field steps have been detected in the current-voltage characteristics of all junctions. Comparison with simulation allows us to attribute these steps to fluxons traveling in the junction for conventional 0 junctions and to fluxon-semifluxon interactions in the case of 0- Josephson junctions.