Spontaneous Friction Switches in Structural Superlubricity

We present results of atomic force microscopy based sliding experiments performed on gold nanoislands on graphite, a material system that exhibits structural superlubricity under ambient conditions [1]. Our measurements reveal a previously undiscovered effect in structural superlubricity: spontaneous switches (i.e., jumps) between two well-defined friction branches. Repeated experiments on the same sample system show that the switching effect disappears in a few weeks, pointing toward a significant influence of contamination. Our work is indicative of non-trivial energy dissipation mechanisms in this elusive ultra-low friction regime.

[1] E. Cihan, S. Ipek, E. Durgun, M.Z. Baykara, Nat. Commun. 7, 12055 (2016).