Fluxon Nucleation By Microwave Currents In Josephson-Junctions

Regular series of microwave absorption lines, observed in the weakest junctions of superconducting single crystals and irregular particles, result from the nucleation of fluxons. This nucleation has a threshold microwave field H c1J , above which the absorption lines broaden into bands of width H 1 - H c1J . The threshold microwave field is anisotropic with respect to the orientation of the junction and decreases with increasing temperature, going to zero at T c . Fluxon nucleation in Josephson junctions may be the major source of RF loss in zero magnetic field at high power levels.