Experimental evidence for supersoliton modes in a long modulated Josephson junction

We report experimental observation of steps in multi-fluxon current-voltage characteristics of a long overlap Josephson junction with a periodic modulation of the critical current density. For the period of the fluxon chain incommensurable with the spatial period of the modulation we observed a low-voltage step in the current-voltage characteristic with the voltage approximately proportional to the incommensurability parameter. This effect is explained in terms of so-called “supersoliton” excitations in spatially modulated Josephson junctions.