Stochastic ratcheting of two dimensional colloids : Directed current and   dynamical transitions
  We present results of molecular dynamics simulations for two-dimensional repulsively interacting colloids driven by a one dimensional asymmetric and commensurate ratchet potential, switching on and off stochastically. This drives a time-averaged directed current of colloids, exhibiting resonance with change in ratcheting frequency, where the resonance frequency itself depends non-monotonically on density. Using scaling arguments, we obtain analytic results that show good agreement with numerical simulations. With increasing ratcheting frequency, we find non-equilibrium re-entrant transitions between solid and modulated liquid phases. 
Dipanjan Chakraborty and Debasish Chaudhuri
cond-mat.soft