Temperature dependence of frictional force in carbon nanotube oscillators

Energy dissipation due to friction in telescopic carbon nanotubes is modeled by molecular dynamics over a wide temperature range. The energy dissipation or the friction force between the inner and outer tubes is strongly related to thermal effects and shows a minimum as temperature increases. At ultra-low temperatures, thermal lubrication, i.e. the reduction in the friction force because of thermal activation, plays a dominant role because energy barriers for the relative translational movement of the concentric nanotubes are so small that the thermally activated jumps effectively reduce the friction force. However, as temperature increases, the thermal jump probability saturates and when the temperature reaches a critical value the dominant phonon frequency exceeds the vibration frequency of the oscillator and more phonons will be excited by the mechanical vibration, which leads to a monotonic increase of the friction force.