Controlling Josephson dynamics by strong microwave fields

We observe several sharp changes in the slope of the current-voltage characteristics CVCs of thin-film ramp-edge Josephson junctions between YBa2Cu3O7− and Nb when applying strong microwave fields. Such behavior indicates an intriguing Josephson dynamics associated with the switching from a parametric excitation regime induced by the magnetic field of the microwave via oscillations of the Josephson critical current to an ac-current-excitation regime triggered by the electric field of the microwave. We propose a model, which describes the observed features on the CVC in terms of microwave-induced multiple switching between running and locked solutions of sine-Gordon equation.