STATIC AND DYNAMIC PROPERTIES OF JOSEPHSON FLUXONS AND THEIR IMPLICATIONS ON CRITICAL CURRENTS, ESPECIALLY IN CUPRATE SUPERCONDUCTORS

Below 1 Tesla pinned JF yield j(c) approximate to j(cJ) less than or e qual to 5 10(7)A/cm(2) with j(cJ) the critical Josephson current. The pinning is due to irregularities in the Josephson junctions (weak link s) consisting of insulating seams of finite length and varying width, e.g., grain or twin boundaries. At higher fields Abrikosov fluxons (AF ) in single crystalline parts may dominate j(c), where j(c) still has to be carried by strong and weak links in series, i.e., by Josephson f luxons (JF) strongly pinned. In addition, the insulating regions at st rong and weak links amount to the largest concentration of insulating material in cuprate superconductors able to pin fluxons. Dynamic prope rties, like, the strong field and frequency dependencies of the surfac e impedance or the fast transition from normal-to-superconducting stat e are solely explainable by fast JF with their low loss insulating cor es. Because j(c) is given by a critical amount of dissipation, the vis cous dynamics of JF- or AF-sliding along weak links play a critical ro le in superconductors containing strong or weak links.(1)