Tuning friction atom-by-atom in an ion-crystal simulator

TL;DR

This study demonstrates control over nanoscale friction by manipulating ion arrangements in a laser-cooled ion crystal, providing insights into atomistic friction models and enabling systematic investigation of friction at the microscopic level.

Contribution

It introduces a synthetic nanofriction system using ion crystals and light fields, allowing precise tuning and exploration of atomistic friction mechanisms.

Findings

Friction can be tuned from maximal to nearly frictionless by ion arrangement.

Strong dependence of friction on structural mismatch appears at just two or three atoms.

The system enables systematic study of friction, including quantum many-body effects.

Abstract

Friction between ordered, atomically smooth surfaces at the nanoscale (nanofriction) is often governed by stick-slip processes. To test long-standing atomistic models of such processes, we implement a synthetic nanofriction interface between a laser-cooled Coulomb crystal of individually addressable ions as the moving object, and a periodic light-field potential as the substrate. We show that stick-slip friction can be tuned from maximal to nearly frictionless via arrangement of the ions relative to the substrate. By varying the ion number, we also show that this strong dependence of friction on the structural mismatch, as predicted by many-particle models, already emerges at the level of two or three atoms. This model system enables a microscopic and systematic investigation of friction, potentially even into the quantum many-body regime.