Phonon and electron contribution to friction force between crystalline solids at low temperatures

摘要

Recent experimental and theoretical findings have shown the static friction force to he absent in the "atomic-dense" contact of two crystalline solids if their lattice constants are incommensurable and the interaction force at the interface does not exceed some critical value. In this case the only friction mechanisms are phonon emission and the excitation of conduction electrons. It is shown in the present work that at low temperatures the phonon contribution to friction might be absent (or very low) because of the quantum-mechanical nature of elementary excitations in a solid. Therefore, incommensurable dielectric crystals can slide almost without friction at sufficiently low temperatures. In contrast, the excitation of conduction electrons in metals results in a non-zero dynamic friction force at any low temperatures. Theoretical estimation of both phonon and electron contribution to the friction force has been conducted.