Nonergodic diffusion of single atoms in a periodic potential

Farina Kindermann, Andreas Dechant, Michael Hohmann, Tobias Lausch, Daniel Mayer, Felix Schmidt, Eric Lutz, Artur Widera

Research output: Contribution to journalArticlepeer-review

31 Citations (Scopus)


Diffusion can be used to infer the microscopic features of a system from the observation of its macroscopic dynamics. Brownian motion accurately describes many diffusive systems, but non-Brownian and nonergodic features are often observed on short timescales. Here, we trap a single ultracold caesium atom in a periodic potential and measure its diffusion. We engineer the particle-environment interaction to fully control motion over a broad range of diffusion constants and timescales. We use a powerful stroboscopic imaging method to detect single-particle trajectories and analyse both non-equilibrium diffusion properties and the approach to ergodicity. Whereas the variance and two-time correlation function exhibit apparent Brownian motion at all times, higher-order correlations reveal strong non-Brownian behaviour. We additionally observe the slow convergence of the exponential displacement distribution to a Gaussian and-unexpectedly-a much slower approach to ergodicity, in perfect agreement with an analytical continuous-time random-walk model. Our experimental system offers an ideal testbed for the detailed investigation of complex diffusion processes.

Original languageEnglish
Pages (from-to)137-141
Number of pages5
JournalNature Physics
Issue number2
Publication statusPublished - 2017 Feb 1
Externally publishedYes

ASJC Scopus subject areas

  • Physics and Astronomy(all)


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