Semifluxons in long Josephson 0-π-junctions -: art. no. 100508

We investigate analytically long Josephson junctions with phase pi-discontinuity points. Such junctions are usually fabricated as a ramp between a superconductor such as YBa2Cu3O7 with d-wave symmetry of the order parameter and an s-wave superconductor such as Nb. From the top, they look like zigzags with pi jumps of the Josephson phase at the corners. These pi jumps, at certain conditions, lead to the formation of half integer flux quanta, which we call semifluxons, pinned at the corners. We derive a version of sine-Gordon equation which describes the dynamics of the Josephson phase in such structures, and obtain an explicit formula that describes the shape of a semifluxon. Some properties of semifluxons are discussed. We propose a way to construct artificial 0-pi-junctions using only s-wave superconductors.