Observation of Aubry transition in finite atom chains via friction

TL;DR

This study experimentally observes the Aubry transition in finite atom chains using cold ions in a periodic potential, linking it to superlubricity and friction phenomena, and confirming theoretical predictions for infinite chains.

Contribution

First experimental observation of the Aubry transition in finite atom chains, demonstrating its relation to superlubricity and validating theoretical models.

Findings

Aubry transition observed in finite ion chains

Critical lattice depth matches infinite chain predictions

Connection established between atomic ordering and friction behavior

Abstract

The highly nonlinear many-body physics of a chain of mutually interacting atoms in contact with a periodic substrate gives rise to complex static and dynamical phenomena, such as structural phase transitions and friction. In the limit of an infinite chain incommensurate with the substrate, Aubry predicted a structural transition with increasing substrate potential, from the chain's intrinsic arrangement free to slide on the substrate, to a pinned arrangement favoring the substrate pattern. To date, the Aubry transition has not been observed. Here, using a chain of cold ions subject to a periodic optical potential we qualitatively and quantitatively establish a close relation between Aubry's sliding-to-pinned transition and superlubricity breaking in stick-slip friction. Using friction measurements with high spatial resolution and individual ion detection, we experimentally observe the Aubry transition and the onset of its hallmark fractal atomic arrangement. Notably, the observed critical lattice depth for a finite chain agrees well with the Aubry prediction for an infinite chain. Our results elucidate the connection between competing ordering patterns and superlubricity in nanocontacts - the elementary building blocks of friction.