The enhancement of current and efficiency in feedback coupled Brownian ratchets

Traditionally, time delay in overdamped Brownian ratchet systems reduces the rectified transport. Strikingly, in our delayed feedback ratchets, which are alternatively switched on and off in dependence of the state of the system, time delay can have significant positive-effects that the average velocity of the coupled ratchets are improved with the presence of the delayed time. Moreover, the anomalous transport can arise and then the negative mobility phenomenon appears by changing the bias force. Meanwhile, the bias force $F$ can facilitate Stokes efficiency of delayed feedback ratchets in the anomalous transport region. Remarkably, it is interesting to find that the coupled ratchets can acquire a series of resonant steps that are induced by frequency locking. More importantly, the optimal delay time can also facilitate Stokes efficiency. The theoretical results may provide a new operating technique in which micro- and nano-motor performance could be improved by the state or information of the delayed feedback coupled ratchets. (paper: classical statistical mechanics, equilibrium and non-equilibrium)