Transport properties in disordered ratchet potentials

The role of disorder in one-dimensional ratchet potentials is investigated by introducing the following: (i) impurities, where a certain fraction of the asymmetric unit cells are replaced bu unit cells with opposite asymmetry, and (ii) randomness, where all unit cells have the same asymmetry, but random size. The relevant color-induced currents are determined and compared with the current of the ideal periodic ratchet potential. Altogether disorder is shown to quench the effectiveness of thermal ratchets, while remarkable transport properties become detectable.