METASTABLE VOLTAGE STATES OF COUPLED JOSEPHSON-JUNCTIONS

We investigate a chain of capacitively coupled Josephson junctions in the regime where the charging energy dominates over the Josephson coup ling, exploiting the analogy between this system and a multidimensiona l crystal. We find that the current-voltage characteristic of the curr ent-driven chain has a staircase shape, beginning with an (insulating) nonzero voltage plateau at small currents. This behavior differs qual itatively from that of a single junction, which should show Bloch osci llations with vanishing dc voltage. The simplest system where this eff ect can be observed consists of three grains connected by two junction s. The theory explains the results of recent experiments on Josephson junction arrays.