Molecular motor that never steps backwards

We investigate the dynamics of a classical pal-tide in a one-dimensional tw o-wave potential composed of two periodic potentials that are time independ ent and of the same amplitude and periodicity. One of the periodic potentia ls is externally driven and performs a translational motion with respect to the other. It is shown that, if one of the potentials is of the ratchet ty pe, translation of the potential in a given direction leads to motion of th e particle in the same direction, whereas translation in the opposite direc tion leaves the particle localized at its original location. Moreover, even if the translation is random, but still has a finite velocity, an efficien t directed transport of the particle occurs.