Friction and chaos: Influence of the damping coefficient on atomic-scale stick-slip on hexagonal crystal lattices

We have numerically investigated the occurrence of long slips when a point mass representing a tip of a solid surface is elastically driven on a hexagonal surface lattice along an arbitrary direction. Tip pathways and slip length histograms are estimated for different values of the damping coefficient $\ensuremath{\gamma}$ defining the duration of the slip phases. The results are compared with a map of all possible ``slip channels'' as obtained analytically with the Prandtl-Tomlinson model in two dimensions. The histograms of the corresponding force drops obtained for different values of $\ensuremath{\gamma}$ could be directly compared with experimental data obtained by friction force microscopy, which would allow us to quantify the energy dissipation in the slip phase in different loading conditions and shed light on quantum effects (phonon and/or electron-hole generation) accompanying sliding friction on the atomic scale.