Absolute negative mobility induced by nonlinear interparticle coupling

We study two inertial Brownian particles with nonlinear coupling in a symmetric periodic potential and subjected to an unbiased harmonic driving in combination with a constant external force. The study focuses on the key role of the nonlinear interaction in inducing the absolute negative mobility. It is revealed that, due to the phase locking effect, with proper strength of nonlinearity, the system may be pushed much more easily into a stable regular trajectory, in which the phase of the relative motion and that of the temporally periodic driving are bounded to a desired phase difference. The overall mobility can be notably negative. The evident connection between the phase locking and the negative mobility is then observed. Furthermore, the robustness under perturbation of external noise can be partly improved in some cases. The way of tuning the collective mobility of a microscopic system via adjusting its internal interactions is thus broadened.