Exploring bidirectional dynamic scaling in condensation dynamics far from equilibrium

The closed-system condensation dynamics of quench-cooled Bose gases has been shown to feature bidirectional dynamic scaling in momentum space, with particle- and energy-conserving transport towards the IR and UV, respectively [1]. Such behavior has been predicted in the context of nonthermal fixed points, and the scaling exponents have been postulated to delineate far-from-equilibrium universality classes. However, the robustness of such behavior with respect to the initial far-from-equilibrium conditions, which is a key ingredient in the theoretical proposals, has remained largely unexplored experimentally. Here we explore the far-from-equilibrium condensation dynamics starting from a novel quantum-chaotic state, which features an isotropic and essentially uniform occupation of low-momentum states with a well-defined high-momentum cutoff. We generate this state by violently driving a noninteracting box-trapped Bose-Einstein condensate in the presence of weak disorder, and then tune the interparticle interactions using a Feshbach resonance to initiate the relaxation dynamics. We exploit our ability to engineer these textbook initial states to study the robustness of the scaling exponents, including how they depend on the energy of the system, the total particle number, and the strength of the interparticle interactions.

[1] J. A. P. Glidden et al., Nat. Phys. 17, 457 (2021)