Description of atomic friction as forced Brownian motion

A theoretical description of friction force microscopy experiments in terms of a forced Brownian motion model is derived on the basis of microscopic considerations. Particular emphasis is put on the discussion of the relevant state variables/collective coordinates and on a realistic description of dissipation and inertia effects by means of comparison with experimental findings. The main new prediction of the model is a non-monotonic dependence of the friction force upon the pulling velocity of the AFM-tip relative to an atomically flat surface. The region around the force maximum can be approximately described by a universal scaling law and should be observable under experimentally realistic conditions.