Observation of breathers in Josephson ladders

We report on the observation of spatially localized excitations in a ladder of small Josephson junctions. The excitations are whirling states which pe rsist under a spatially homogeneous force due to the bias current. These st ates of the ladder are visualized using a tow temperature scanning laser mi croscopy. We also compute breather solutions with high accuracy in correspo nding model equations. The stability analysis of these solutions is used to interpret the measured patterns in the I-V characteristics.