Nonergodic Diffusion of Single Atoms in a Periodic Potential

TL;DR

This study investigates the diffusion behavior of a single atom in a periodic potential, revealing non-ergodic dynamics and subdiffusive behavior, with implications for understanding microscopic transport processes.

Contribution

It demonstrates control over diffusion regimes and identifies non-ergodic dynamics in single-atom diffusion within engineered periodic potentials.

Findings

Step size distribution exhibits exponential decay.

Non-ergodic behavior observed over long times.

Model aligns with continuous time random walk with exponential waiting times.

Abstract

Diffusion is a central phenomenon in almost all fields of natural science revealing microscopic processes from the observation of macroscopic dynamics. Here, we consider the paradigmatic system of a single atom diffusing in a periodic potential. We engineer microscopic particle-environment interaction to control the ensuing diffusion over a broad range of diffusion constants and from normal to subdiffusion. While one- and two-point properties extracted from single particle trajectories, such as variance or position correlations, indicate apparent Brownian motion, the step size distribution, however, shows exponentially decaying tails. Furthermore non-ergodic dynamics is observed on long time scales. We demonstrate excellent agreement with a model of continuous time random walk with exponential distribution, which applies to various transport phenomena in condensed or soft matter with periodic potentials.