Bonn 2025 – wissenschaftliches Programm

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MO: Fachverband Molekülphysik

MO 12: Poster – Cold Atoms and Molecules, Matter Waves (joint session Q/A/MO)

MO 12.37: Poster

Dienstag, 11. März 2025, 14:00–16:00, Tent

Reaction-Diffusion Dynamics of Quantum Gases — •Hannah Lehr, Igor Lesanovsky, and Gabriele Perfetto — Institut für Theoretische Physik, Universität Tübingen, Auf der Morgenstelle 14, 72076 Tübingen, Germany

We consider the dynamics of quantum gases underlying coherent motion as well as dissipative reactions. For Fermions we discuss e.g., k-body losses kA→∅. In this case the universality lies within the long time decay of the particle density. For Bosons we consider also particle creating processes as branching A→ A+A. The competition between the latter and single body decay and coagulation A+A→ A leads to an absorbing state phase transition in the stationary state. Our goal is to understand how quantum effects impact on the universality class of the transition.

We tackle these problems combining a variety of methods ranging from kinetic large-scale equations via the time-dependent generalized Gibbs ensemble method (TGGE), and Keldysh field-theory diagrammatic expansion. Specifically, for the Fermi gas under weak k-body losses we find long-time decay for the density of particles different from mean field. For the Bose gas, we observe a rich stationary phase diagram different from the classical counterpart of the model.

Our findings show that quantum effects impact on large-scale universal behaviour leading to novel universality classes compared to classical physics. These results are experimentally relevant since they directly connect to cold-atomic processes involving dissipative processes such as particle losses and creation.

Keywords: time dependent generalized Gibbs ensamble; Keldysh field theory; absorbing state phase transition; non-equlibrium many body quantum systems; dissipative quantum gases