Velocity Dependence of Moire Friction

Friction force microscopy experiments on moire superstructures of graphene-coated platinum surfaces demonstrate that in addition to atomic stick-slip dynamics, a new dominant energy dissipation route emerges. The underlying mechanism, revealed by atomistic molecular dynamics simulations, is related to moire ridge elastic deformations and subsequent relaxation due to the action of the pushing tip. The measured frictional velocity dependence displays two distinct regimes: (i) at low velocities, the friction force is small and nearly constant; and (ii) above some threshold, friction increases logarithmically with velocity. The threshold velocity, separating the two frictional regimes, decreases with increasing normal load and moire superstructure period. Based on the measurements and simulation results, a phenomenological model is derived, allowing us to calculate friction under a wide range of room temperature experimental conditions (sliding velocities of 1-104 nm/s and a broad range of normal loads) and providing excellent agreement with experimental observations.

Automated summary

Friction force microscopy experiments on moire superstructures of graphene-coated platinum surfaces reveal a new dominant energy dissipation route related to moire ridge elastic deformations. The frictional velocity dependence exhibits two distinct regimes, with a threshold velocity separating them that decreases with increasing normal load and moire superstructure period. A phenomenological model based on measurements and simulations accurately predicts friction under various room temperature experimental conditions.