Atomistics of superlubricity

Friction is a phenomenon observed ubiquitously in daily life, yet its nature is complicated. Friction between rough surfaces is considered to arise primarily because of macroscopic roughness. In contrast, interatomic forces dominate between clean and smooth surfaces. Superlubricity, where friction effectively becomes zero, occurs when the ratio of lattice parameters in the pair of surfaces becomes an irrational number. Superlubricity has been found to exist in a limited number of systems, but is a very important phenomenon both in industry and in mechanical engineering. New atomistic research on friction is under way, with the aim of refining theoretical models that consider interactions between atoms beyond mean field theory and experiments using ultrahigh vacuum non-contact atomic force microscopy. Such research is expected to help clarify the nature of microscopic friction, reveal the onset conditions of friction and superlubricity as well as the stability of superlubricity, discover new superlubric systems, and lead to new applications.