Nonlinear effects in coupled Josephson devices

The nonlinear equations for two magnetically coupled Josephson point junctions driven by a current source in the presence of an applied field and including capacitive and dissipative currents have been accurately solved numerically. The asymptotic periodic behavior is used to determine the static current-voltage characteristic, which has three parts connected by constant current steps - a zero-voltage part in which the phase differences of the junctions tend to constant values, an intermediate-voltage part in which current and voltage slowly "beat" between the junctions and a high-voltage part approaching the constant resistance line. The dynamic characteristic for slowly increasing and decreasing currents shows hysteresis and the positions of the voltage jumps are sensitive to the applied field.