Velocity dependence of atomic-scale friction: A comparative study of the one- and two-dimensional Tomlinson model

摘要

We present a comparative analysis of the velocity dependence of atomic-scale friction for the Tomlinson model, at zero and finite temperatures, in one and two dimensions, and for different values of the damping. Combining analytical arguments with numerical simulations, we show that an appreciable velocity dependence of the kinetic friction force F_(fric), for small scanning velocities v_s (from 1 nm/s to μm/s), is inherent in the Tomlinson model. In the absence of thermal fluctuations in the stick-slip regime, it has the form of a power-law F_(fric)-F_0 ∝ v_s~β with β=2/3, irrespective of dimensionality and value of the damping. Since thermal fluctuations enhance the velocity dependence of friction, we provide guidelines to establish when thermal effects are important and to which extent the surface corrugation affects the velocity dependence.