Driven Ratchets with Disordered Tracks

The stochastic motion of ratchets is studied in the context of driven or pumped two-state models. For completely ordered tracks, the ratchets can be characterized both by an effective drift velocity and an effective diffusion coefficient on large scales. These properties are strongly perturbed by the presence of frozen disorder or defects along the tracks. Depending on the defect concentration and on the transition rates between the two states, the ratchets now exhibit several scaling regimes with anomalous transport properties.