Onset of incommensurate interfacial instability in a minimal model of dry friction.

We present a minimal model of dry friction between two incommensurate interfaces sliding at high relative velocity. Many of the features of the friction force for the full two-dimensional many-body dynamical system-particularly in the sub-critical velocity regime-are captured by our one-dimensional Einstein model, where the motion of a typical interfacial atom is constrained to be vertical to the sliding plane. Beyond the linear response of force versus sliding velocity, the anharmonic Einstein model predicts a doublet resonance peak, whereupon a catastrophe in the model signals the onset of a plastic deformation mechanism for frictional sliding, namely, the instability of the interface.