Charge density wave surface phase slips and non-contact nanofriction

TL;DR

This paper introduces a nanoscale mechanism for mechanical dissipation peaks caused by charge-density-wave phase slips during atomic force microscopy, explaining experimental observations in CDW materials like NbSe2.

Contribution

It proposes a new local surface phase slip mechanism for dissipation peaks in AFM measurements on CDW surfaces, supported by numerical simulations.

Findings

Local 2π phase slips cause hysteresis and dissipation peaks.

Numerical simulations match experimental data on NbSe2.

Mechanism applicable to other CDW systems.

Abstract

Bulk electrical dissipation caused by charge-density-wave (CDW) depinning and sliding is a classic subject. We present a novel 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 NbSe$_2$; other candidate systems in which similar effects should be observable are also discussed.