NONLINEAR FRICTION IN THE PERIODIC STICK-SLIP MOTION OF COUPLED OSCILLATORS

We suggest that coupling-induced orbit hopping is one possible mechani sm for stick-slip dynamics. This mechanism is dominant in the highly n onlinear regime. Our example is a one-dimensional array of nonlinearly coupled oscillators subject to a strong periodic potential. The nonli near dynamics leads to a fundamentally different friction law, in part icular when the driving force is barely larger than the minimal force needed to start motion. We fmd a dramatic increase in the friction coe fficient of the array compared to that of a single uncoupled oscillato r, even though the same constant force f is applied to each oscillator in the array. The sliding friction coefficient eta is found to diverg e as eta proportional to (kappa-kappa(C))(-1/2), where kappa(C), is th e critical value of the a coupling constant kappa. The coefficient eta also grows linearly with the number of elements in the array N and sh ows dynamical transitions as the external force f applied to each of t he oscillators is increased.