  Structural superlubricity is an intriguing physical phenomenon, whereby
sliding at a structurally incommensurate, atomically flat interface yields
vanishingly small friction forces. Despite its recent experimental validation,
critical questions remain regarding the physical limitations of the concept. In
particular, it is not known whether the ultra-low friction state would persist
at high sliding speeds relevant for practical, small-scale mechanical systems.
Here, we perform sliding experiments via atomic force microscopy on gold
nanoislands on graphite at increasing speeds, extracting interfacial friction
forces under ambient conditions. A heterodyne detection methodology enables the
extraction of extremely weak friction signals buried deep in the noise,
revealing that the structurally superlubric regime extends over 100,000 nm/s
with minimal changes in friction force, spanning three orders of magnitude in
sliding speed. Our results contribute significantly to the pursuit of
functional, superlubric mechanical devices.
