A phenomenological model for high-frequency dynamics of double-barrier (SINIS) Josephson junctions

Double-barrier Josephson junctions, with outer electrodes of superconductin g Nb and a central thin layer of non-superconducting Al, are being develope d as self-shunted junctions for high-frequency superconducting integrated c ircuits. This paper presents a simplified phenomenological model of the beh aviour of such junctions (often called SINIS, for superconductor-insulator- normal-insulator-superconductor) based on the resistively shunted junction model, using Josephson coupling between the layers and the time-dependent G inzburg-Landau equation to describe the dynamics of the weak induced energy gap in the Al layer. This analysis shows how non-hysteretic I-V characteri stics can be obtained but suggests some limitations in their high-frequency performance. Predictions for critical current generally agree with prior e xperiments. The technological implications of this model are discussed.