Superconducting critical currents for thick, clean superconductor—normal-metal—superconductor junctions

Abstract

Superconducting critical currents have been studied for superconductor---normal-metal---superconductor ($S\ensuremath{-}N\ensuremath{-}S$) junctions as a function of temperature, magnetic field, and thickness in order to determine the spatial variation of the superconducting pair potential in the normal-metal region. Emphasis is placed on the thick, clean limit for the normal metal. The temperature dependence of ${J}_{c}$ obeys predictions based on the de Gennes-Werthamer theory, and the magnitude of ${J}_{c}$ is reasonable. In a high magnetic field, ${J}_{c}$ falls exponentially with increasing magnetic field, indicating that the inverse of the decay length of the order parameter, ${K}_{N}^{\ensuremath{-}1}$, is approximately linear in $H$.