Evidence for vortex splitting at the grain boundary in long YBa2Cu3O7−δ grain boundary junctions

We investigated the current-voltage characteristics and the critical current density (Jc) of a YBa2Cu3O7−δ grain boundary (GB) long Josephson junction with respect to magnetic field (H) under different application directions. When H is rotated within the bc-plane of the film, a small peak of Jc is observed when H is parallel to the c-axis, which denotes that there are some residual c-axis dislocations in the GB. When H is rotated within the ac-plane, some vortex-flow steps can be observed in the current-voltage curve at a high inclination angle of H. The vortex-flow step becomes smaller and wider with the decreasing angle between H and the c-axis. These results are a clear demonstration of vortex splitting at the GB plane in YBa2Cu3O7−δ GB long Josephson junctions.