Proximity effect in YBa2Cu3O7/Y0.6Pr0.4Ba2Cu3O7/YBa2Cu3O7 junctions

Abstract

We report critical-current measurements in all high-${\mathit{T}}_{\mathit{c}}$ superconducting-normal-superconductor junctions using ${\mathrm{Y}}_{0.6}$ ${\mathrm{Pr}}_{0.4}$ ${\mathrm{Ba}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_7$ (with ${\mathit{T}}_{\mathit{c}\mathit{N}}$=40 K) as the normal metal. Above ${\mathit{T}}_{\mathit{c}\mathit{N}}$, we find a clear exponential dependence of ${\mathit{I}}_{\mathit{c}}$ on the thickness of the barrier which is characteristic of the proximity effect. The order-parameter decay length is about 120 Å for T>60 K, and it diverges as ${\mathit{T}}_{\mathit{c}\mathit{N}}$ is approached. We estimate that ${\xi }_0$ for this material is 80±25 Å.