Controlling sliding velocity by mode locking at nanoscale solid surfaces with lubricants

Driven dynamics and kinetic frictional phenomena at nanoscale solid-solid surfaces with lubricants in the presence of both dc and ac driving forces are studied numerically. Using a lattice model which consists of two rigid substrates and a monolayer of lubricant molecules, we found mode locking phenomena, that is, the dc sliding velocity is locked to be fixed values concerning the ac driving frequency for a finite range of the dc driving force. We discuss the details of the mode locking and the kinetic frictional force in connection with the control of friction at nanoscale.