Peculiarities of Brownian Motion Depending on the Structure of the Periodic Potentials

Transport of over-damped Brownian particles in periodic double-barrier potentials is studied in the absence and under the influence of a constant tilting force. Depending on the value of the tilt the transport of particles in potentials with two barriers per period has in general character similar to that in simple potentials, exhibiting at the same time in certain parameter regions qualitatively different features. As the most unexpected result it is found that diffusion coefficient can have two maxima. It is also shown that in the wide range of tilting force the transport can be realized through two different Poissonian processes, having at a certain tilt a resonant-like enhancement of the coherence. (author)