Evidence for contact delocalization in atomic scale friction

TL;DR

This paper presents a two-spring model with ultra-low tip mass to explain complex atomic stick-slip behavior in FFM, revealing contact delocalization effects that align with recent experimental observations.

Contribution

It introduces a novel two-spring model demonstrating contact delocalization in atomic-scale friction, providing new insights into FFM measurements and contact mechanics.

Findings

Presence of fine structure in atomic stick-slip motion.

Tip apex can be delocalized, affecting measured friction.

Model aligns with recent experimental data.

Abstract

We analyze an advanced two-spring model with an ultra-low effective tip mass to predict nontrivial and physically rich 'fine structure' in the atomic stick-slip motion in Friction Force Microscopy (FFM) experiments. We demonstrate that this fine structure is present in recent, puzzling experiments. This shows that the tip apex can be completely or partially delocalized, thus shedding new light on what is measured in FFM and, possibly, what can happen with the asperities that establish the contact between macroscopic sliding bodies.