Atomic rheology of gold nanojunctions

TL;DR

This study uses advanced atomic force microscopy to explore the complex rheological behavior of gold nanojunctions at atomic scales, revealing a transition from elastic to viscous-like states and highlighting unique dissipative phenomena.

Contribution

It introduces a novel experimental approach combining electrical and rheological measurements to analyze atomic-scale gold junctions, uncovering their non-linear rheology and fluidization behavior.

Findings

Transition from elastic to viscous-like behavior with increasing deformation

Capillary attraction observed in fluidized state

Unexpected dissipative behavior in defect-free metallic junctions

Abstract

Despite extensive investigations of dissipation and deformation processes in micro- and nano- sized metallic samples, the mechanisms at play during deformation of systems with ultimate, molecular size remain elusive. While metallic nanojunctions, obtained by stretching metallic wires down to the atomic level are a system of choice to explore atomic scale contacts, it has not been possible up to now to extract the full equilibrium and out of equilibrium rheological flow properties of matter at such scales. Here, by using a quartz-tuning fork based Atomic Force Microscope (TF-AFM), we combine electrical and rheological measurement on angstr\"om-size gold junctions to study the non linear rheology of this model atomic system. By submitting the junction to increasing sub-nanometric deformations we uncover a transition from a purely elastic regime to a plastic, and eventually to a viscous-like fluidized regime, akin to the rheology of soft yielding materials, though orders of magnitude difference in length scale. The fluidized state furthermore highlights capillary attraction, as expected for liquid capillary bridges. This shear fluidization cannot be captured by classical models of friction between atomic planes, pointing to unexpected dissipative behavior of defect-free metallic junctions at the ultimate scales. Atomic rheology is therefore a powerful tool to probe the structural reorganization of atomic contacts.