Mainz 2017 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 57: Ultracold Atoms II
Q 57.4: Talk
Friday, March 10, 2017, 15:15–15:30, P 104
Nonergodic diffusion of single atoms in a periodic potential — •Daniel Adam1, Farina Kindermann1, Andreas Dechant2, Tobias Lausch1, Daniel Mayer1, Felix Schmidt1, Steve Haupt1, Michael Hohmann1, Nicolas Spethmann1, Eric Lutz2, and Artur Widera1 — 1TU Kaiserslautern, Department of Physics, Kaiserslautern, Germany — 2Friedrich-Alexander-Universität, Department of Theoretical Physics, Erlangen, Germany
Diffusion is ubiquitous in nature, and related models are essential to many fields in science, technology and society, including life sciences, traffic or financial market theory. The most prominent model for diffusion is Brownian motion. The hallmarks of this are a linearly increasing mean squared displacement (MSD); a Gaussian distributed step distance distribution; a stationary value for the autocorrelation function of single particle trajectories; and established ergodicity. Here, we engineer a system of a single atom in a periodic potential, which is coupled to a photon bath. We observe diffusion of the atom in the lattice, driven by random photon scattering events. While the dynamics exhibits a linear increase of the MSD for all times, we find that ergodicity is not established even for long timescales. Moreover, we observe a different timescale on which the step distribution approaches Gaussianity. Our experimental results for equilibrium systems are in excellent agreement with analytical predictions of a continuous time random walk model with exponential distance and waiting time distribution. Our results may be helpful for the interpretation of related observations in biological systems.