Proximity effect in ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$/${\mathrm{YBa}}_2$(${\mathrm{Cu}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Co}}_{\mathit{x}}$${)}_3$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ /${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}}$δ junctions: From the clean limit to the dirty limit the clean limit to the dirty limit with pair breaking

We report on the proximity effect observed in ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$/${\mathrm{YBa}}_2$(${\mathrm{Cu}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{Co}}_{\mathit{x}}$ ${)}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ /${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ junctions in an edge-junction geometry where x=0.04, 0.07, and 0.14. The temperature, thickness, and doping dependence of the critical current of the junctions can be well described by the proximity-effect theory, due to very little interface resistance. We observed a crossover from the clean limit to the dirty limit behavior where a pair-breaking scattering time ${\mathrm{\tau }}_{\mathrm{pb}}$=6×${10}^{\mathrm{-}14}$ sec, consistent with short-range magnetic fluctuations in the barrier, was found.