We report experiments of atomic stick-slip friction on graphite as an explicit function of surface temperature between 100 and 300 K under ultrahigh vacuum conditions. A statistical analysis of the individual stick-slip events as a function of the velocity reveals an agreement with the thermally activated Prandtl-Tomlinson model at all temperatures. Taking into account an explicit temperature-dependence of the attempt frequency all data points collapse onto one single master curve.

The main challenge in predicting sliding friction is related to the complexity of highly nonequilibrium processes, the kinetics of which are controlled by the interface temperature. Our experiments reveal a nonmonotonic enhancement of dry nanoscale friction at cryogenic temperatures for different material classes. Concerted simulations show that it emerges from two competing processes acting at the interface: the thermally activated formation as well as rupturing of an ensemble of atomic contacts. These results provide a new conceptual framework to describe the dynamics of dry friction.

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