Charge-density-wave surface phase slips and noncontact nanofriction

Bulk electrical dissipation caused by charge-density-wave (CDW) depinning and sliding is a classic subject. We present a local, nanoscale mechanism describing the occurrence of mechanical dissipation peaks in the dynamics of an atomic force microscope tip oscillating above the surface of a CDW material. Local surface 2 pi slips of the CDW phase are predicted to take place, giving rise to mechanical hysteresis and large dissipation at discrete tip surface distances. The results of our static and dynamic numerical simulations are believed to be relevant to recent experiments on NbSe2; other candidate systems in which similar effects should be observable are also discussed.