Current oscillations in near-commensurate systems

The phenomena of current oscillations (CO) in response to a dc field is studied by the one-dimensional damped and field-driven sine-Gordon equation. For low damping we find that kink-antikink pairs survive collisions and CO through periodic boundaries is possible. For large damping CO is possible if the field is inhomogeneous, e.g., at contacts, creating kink-antikink pairs periodically. The results can account for data on charged-density waves and vortex lattice motion in superconducting films and annular Josephson junctions.