Velocity tuning of friction with two trapped atoms

Nature Physics 11, 915?919 (2015)

Dorian Gangloff, Alexei Bylinskii, Ian Counts, Wonho Jhe & Vladan Vuleti?

Our ability to control friction remains modest, as our understanding of the underlying microscopic processes is incomplete1, 2, 3. Atomic force experiments4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 have provided a wealth of results on the dependence of nanofriction on structure5, 6, velocity7, 8, 9, 10 and temperature11, 12, 13, but limitations in the dynamic range, time resolution, and control at the single-atom level have hampered a description from first principles3. Here, using an ion-crystal system with single-atom, single-substrate-site spatial and single-slip temporal resolution15, 16, we measure the friction force over nearly five orders of magnitude in velocity, and contiguously observe four distinct regimes, while controlling temperature and dissipation. We elucidate the interplay between thermal and structural lubricity for two coupled atoms, and provide a simple explanation in terms of the Peierls?Nabarro potential17. This extensive control at the atomic scale enables fundamental studies of the interaction of many-atom surfaces, possibly into the quantum regime.