Effect of bias electrodes on characteristics of long Josephson junctions

We have investigated the characteristics of long Josephson junctions with geometries containing several entry points for current. A single device can be biased at a junction end, at the center, or at both ends depending on the choice of electrodes. A branch of the current-voltage curves and the dependence of maximum DC Josephson current on an external magnetic field may be symmetric or asymmetric for a single device depending on the current feed points. In all of the cases, at a given current bias on this branch, the junction voltage increases with the application of an external magnetic field beyond a critical field. This is the minimum magnetic field necessary to introduce fluxons into the junction. A Simple model for tunnel current distribution is used to explain the experimental data. For an asymmetrically biased junction, we show that the effective dynamic resistance exhibited for bias at a boundary is either 0 or . This suggests that the dynamic resistance of the device may be varied by merely moving the bias feed point along the junction.