JOSEPHSON TUNNELING FOR MAGNETIC-FIELDS PERPENDICULAR TO DISCRETE NB JUNCTIONS - IMPLICATIONS FOR THE IRREVERSIBILITY CROSSOVER IN HIGH-TEMPERATURE SUPERCONDUCTORS

It was recently suggested that coupling between the superconducting Cu-O bilayer or trilayer units in the highly anisotropic, high-temperature superconductors (HAHTS) can be described by incoherent Josephson tunneling. This paper confirms the assumed inverse dependence of the coupling energy on field, H, through measurements of the zero-bias resistance of discrete, high-quality, thin-film Nb Josephson junctions. This 1/H dependence was used to explain the flux-motion-induced broadening of resistive transitions in HAHTS for equivalent geometry with H parallel to the c axis. The Nb junction results also unambiguously confirm another recent suggestion: that field-induced dissipation can occur in Josephson junctions without the motion of vortices from an externally applied field, which in this case are pinned in the Nb electrodes.