Disorder Induced Diffusive Transport In Ratchets
  The effects of quenched disorder on the overdamped motion of a driven particle on a periodic, asymmetric potential is studied. While for the unperturbed potential the transport is due to a regular drift, the quenched disorder induces a significant additional chaotic ``diffusive'' motion. The spatio-temporal evolution of the statistical ensemble is well described by a Gaussian distribution, implying a chaotic transport in the presence of quenched disorder. 
M. N. Popescu, C. M. Arizmendi, A. L. Salas-Brito, and F. Family