INTERNAL RESONANCES IN PERIODICALLY MODULATED LONG JOSEPHSON-JUNCTIONS

Current-voltage (I - V) characteristics of long Josephson junctions wi th a periodic lattice of localized inhomogeneities are studied. The in teraction between the moving fluxons and the inhomogeneities causes re sonant steps in the IV-curve. Some of these steps are due to a synchro nization to resonant Fiske modes in the sub-junctions formed between t he inhomogeities. The voltage positions of the resonant steps oscillat e as function of the applied magnetic field with a period correspondin g to the inclusion of one magnetic flux quantum, Phi(0) = h/2e, per su b-junction. qualitative explanation that takes into account the intera ction between the resonance in the sub-junction and the magnetic flux density waves excited in the whole junction is given.