Phase-locked states in the system of two capacitively coupled Josephson junctions

The dynamics of two underdamped Josephson junctions coupled by a capacitanc e is studied analytically and numerically. Two types of stationary states a re found for the system. Averaged voltages across the junctions have the sa me (nonzero) values for the first type of states, while for the second type the voltage across one of the junctions is equal to zero. The region of th e synchronized dynamics is narrow and depends on the way of the current var iation. The current-voltage characteristics shows negative differential res istance for the second type of states. The switching between different stat es by variation of applied currents is observed. Existence conditions for t he phaselocking and;parameters of synchronized oscillations are obtained an alytically. The result of numerical calculations agrees with theoretical pr edictions.