Analog simulation on enhanced AC Josephson effect for a junction driven by RF-current source

The ac Josephson effect for a current-driven Josephson junction enhanced by a non-monochromatic input signal is studied based on an analog simulation. The obtained rf-induced step-height in the current-voltage characteristic which is a measure of this effect suggest that the use of either a pulse train or a biharmonic consisting of fundamental and second harmonic sinusoidal functions is effective for the enhancement, if compared to a monochromatic signal drive. It is revealed that the individual phase locking between the rf-signal and the Josephson oscillation is much more stabilized by use of the pulse train-like signal and can be explained qualitatively by a pendulum motion, ie., the relatively slow motion of the pendulum near the position of rest.