Giant enhancement of diffusion and particle selection in rocked periodic potentials

Abstract

We investigate the motion of an overdamped Brownian particle in a periodicpotential with weak thermal noise and a time-periodic unbiased (i.e. ⟨F(t)⟩ = 0) external driving force F(t). By introducingappropriate “waiting-periods”, where F(t) vanishes, an arbitrarily strongenhancement of diffusion in a symmetric potential is possible. In asymmetric periodic potentials (ratchets) the net flux of particles can be directed in both directions, even in the absence of thermal noise. For finite temperatures we observe and explain additional, pure-noise–induced flux reversal phenomena.