SIMULTANEOUS SWITCHING ON VERTICALLY STACKED JOSEPHSON-JUNCTIONS WITHVERY THIN INTERMEDIATE ELECTRODE

We have demonstrated vertically stacked Josephson junctions with very thin superconductors for the intermediate electrode. The gap voltage o f a thin film decreases as the thickness decreases, but the decrease o f the energy gap does not worsen the quality of the junction. In the d ouble junction, simultaneous switching between the lower and upper jun ctions is observed. Although simultaneous switching is also observed i n the series-connected Josephson junction, we have found some differen ces between them and have investigated the condition of simultaneous s witching in the double junction.