Observation of Relaxation Stages in a Nonequilibrium Closed Quantum System: Decaying Turbulence in a Trapped Superfluid

Abstract

The dynamics of non-equilibrium closed quantum systems and their route to thermalization are of fundamental interest to several fields, from cosmology to particle physics. However, a comprehensive description of non-equilibrium phenomena still presents a significant challenge. In this work, we report the observation of distinct stages during the relaxation of the decaying turbulence in trapped Bose-Einstein condensates. Our findings show a direct particle cascade from low to high momenta, a consequence of the energy injection in the system, exhibiting a characteristic universal scaling. This stage is followed by an inverse particle cascade responsible for repopulating the previously depleted condensate. Both cascades can be explained through self-similar solutions provided by wave turbulence theory. These findings provide important insights into the relaxation stages of out-of-equilibrium quantum many-body systems.

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• An Equation of State for Turbulence in the Gross-Pitaevskii model
• Anomalous non-thermal fixed point in a quasi-two-dimensional dipolar Bose gas
• Evolution of density variations in a trapped atomic superfluid driven into turbulence
• Decaying superfluid turbulence near an anomalous non-thermal fixed point
• Metastability, chaos and spectrum tomography for Bose-Hubbard rings and chains