Nanotribology of Commensurate and Incommensurate Colloidal Monolayers on Periodic Surfaces

Abstract

Whenever two adjacent bodies are brought into relative motion, friction occurs. Despite its broad implications to our daily life and technical applications, many aspects of friction are only poorly understood. This particularly applies to conditions, where two atomically smooth surfaces are sliding on top of each other. Using a colloidal monolayer which is driven across a structured surface, we can confirm the dominating role of topological solitons during this process. In addition, we provide experimental evidence for the Aubry transition which predicts a frictionless sliding at incommensurate conditions and for finite substrate corrugations. Our results do not only reveal the subtle structural changes of the monolayer to avoid friction but also a sharp transition from a fully superlubric to a strongly pinned state when the contact strength between the surfaces is increased.