Superslipperiness at low temperatures: Quantum mechanical aspects of solidstate friction

It has recently been shown that there is no static friction in a contact of atomically hat crystalline solids provided the periods of their lattices a re incommensurate and they are interacting weakly. In the present Letter, i t is shown that, at low temperatures, the phonon contribution to the coeffi cient of friction can be very small also, by virtue of the quantum mechanic al nature of the elementary excitations in a solid. Incommensurate dielectr ic crystals could therefore slip at low temperatures practically without fr iction.