ATOMIC-SCALE FRICTION - WHAT CAN BE DEDUCED FROM THE RESPONSE TO A HARMONIC DRIVE

In this Letter we investigate the response of a confined chain to a ha rmonic driving force. A model is introduced which mimics recent measur ements on friction using surface forces apparatus. The model predicts a critical driving amplitude below which the response is linear. For h igher amplitudes the system exhibits a nonlinear behavior and shear th inning. A novel origin for the thinning is proposed which stems from e nergy dissipation due to stick-slip motion and the transition to smoot h sliding. We establish relationships between the microscopic paramete rs of the system and phenomena observed in rheology and tribology. [S0 031-9007(98)06799-4].