On the amplification of diffusion on piecewise linear potentails by   direct current
  The diffusive motion of overdamped Brownian particles in tilted piecewise linear pontentials is considered. It is shown that the enhancement of diffusion coefficient by an external static force is quite sensitive to the symmetry of periodic potential. Another new effect found is that the factor of randomness as a function of the tilting force exibits a plateau-like behaviour in the region of low temperatures. 
Els Heinsalu, Risto Tammelo, Teet Ord