The roles of ratchet in transport of two coupled particles

The properties of a ratchet system rectifying the random motion of two harmonically coupled particles with arbitrary coupling strengths are studied via Langevin simulations. In comparison with the result of single particle, our results show that the average center-of-mass velocity vc of two particles is larger than the average velocity v1 of single particle in the rocking ratchet for low-to-moderate noise intensities, however, vc<v1 in the flashing ratchet. The former is due to the decrease of effective barrier that the center-of-mass of two particles feels, and the latter is because of the distance of two diffusing particles across the nearest barrier increasing effectively. Numerical results are performed for a larger parameter regime and the validation of the proposed effective potential is illustrated.