Bonn 2025 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 25: Poster – Cold Atoms and Molecules, Matter Waves (joint session Q/A/MO)

Q 25.44: Poster

Tuesday, March 11, 2025, 14:00–16:00, Tent

Langevin dynamics of a Bose gas coupled to a small heat bath — •Carsten Henkel and Sasha Roewer — Universität Potsdam, Institut für Physik und Astronomie

In an elongated, quasi-one-dimensional trap, a degenerate Bose gas is formed by atoms in the lowest quantum state of the ``radial'' confinement. Atoms in higher states can provide a heat bath which is, however, not much larger compared to the degenerate gas. We study with the help of Langevin dynamics (stochastic Gross-Pitaevskii equation) the evolution of the complex order parameter, taking into account the exchange of energy and particles with the heat bath. Curiously, as the heat bath gets smaller, its temperature drops, and the Bose gas is more degenerate. At the same time, temperature fluctuations are larger. Thermodynamically relevant quantities like the internal energy are extracted from the simulations. We also explore non-equilibrium situations with an externally imposed temperature difference.

Keywords: strong coupling; open system