Dynamical Transitions in Correlated Driven Diffusion in a Periodic Potential

The diffusion of a two-dimensional array of particles driven by a constant force in the presence of a periodic external potential exhibits a hierarchy of dynamical phase transitions when the driving force is varied. This behavior can be explained by a simple phenomenological approach which reduces the system of strongly interacting particles to weakly interacting quasiparticles (kinks). The richness of the strongly coupled system is, however, not lost because, contrary to a single Brownian particle, the array shows an hysteretic behavior even at nonzero temperature. The present investigation can be viewed as a first step toward understanding nanotribology. [S0031-9007(97)02426-5] The diffusion of a Brownian particle, driven by an external force and subjected to a periodic potential, is a situation which arises in several fields of science [1] such as solidstate physics, surface physics [2], chemical physics, and even communication theory. It is now well understood and provides a simple example of an out-of-equilibrium phase transition, between a locked and a running state. The case of many interacting particles is even more interesting because collective effects modify qualitatively the picture giving rise, in some parameter range, to a dynamical state which is very reminiscent of a traffic jam at the atomic scale. We discuss here this behavior in the context of solid-state friction because it provides a typical example which may be amenable to experimental tests, but the basic ingredients required to observe the phenomenon are simple