Multi-fluxon steps in long Josephson junctions and their application to oscillators

Studies of long NbN Josephson junctions of the overlap type in the presence of an external magnetic field show constant voltage steps, of the Fiske type, and large voltage steps. The latter are attributed to multifluxon resonances within the cavity of the junction. The multifluxon steps correspond to bunches of fluxons introduced in the junction because the junction electrode thicknesses are comparable to the penetration depth. These steps are very sharp and they have large current amplitudes. When biased at such constant voltage steps the device can be a resonant mode oscillator. The power and frequency will be determined by the mode of fluxon motion inside the junction.