Interaction induced by nonuniform self-fields in stacks of two long Josephson junctions

We fabricated and tested devices consisting of two long stacked Josephson j unctions with direct access to the intermediate electrode, whose thickness is smaller than London penetration depth XL. The electrodes are patterned s o that the junctions can be independently biased in the overlap configurati on. In the absence of an external magnetic held, we measured the critical c urrent of one junction in the stack as a function of the bias current in th e other junction, while the latter was either in the zero voltage state or in the McCumber state. The results indicate that mutual interaction takes p lace anyway, i.e. when both the junctions or only one of them is in the zer o voltage state. To account for the observed phenomena we propose a model t hat takes into account the nonuniform self-fields generated by the bias cur rents in this special three-terminal device.