Kinks and Nanofriction: Structural Phases in Few-Atom Chains

TL;DR

This study investigates how structural phases in few-atom chains influence nanofriction, revealing a transition between high-friction and low-friction states driven by kink dynamics, with implications for nanocontact control.

Contribution

The paper experimentally demonstrates the role of kinks in the commensurate-incommensurate transition affecting nanofriction in trapped-ion chains.

Findings

Identification of two frictional phases: high and low friction.

Kink velocity increases with lattice incommensurability.

Direct atom-by-atom tracking of kink propagation.

Abstract

The frictional dynamics of interacting surfaces under forced translation are critically dependent on lattice commensurability. Performing experiments in a trapped-ion friction emulator, we observe two distinct structural and frictional phases: a commensurate high-friction phase where the ions stick-slip simultaneously over the lattice, and an incommensurate low-friction phase where the propagation of a kink breaks that simultaneity. We experimentally track the kink's propagation with atom-by-atom and sub-lattice site resolution, and show that its velocity increases with commensurability. Our results elucidate the commensurate-incommensurate transition and the connection between the appearance of kinks and the reduction of friction in a finite system, with important consequences for controlling friction at nanocontacts.