Observation of an Inverse Turbulent-Wave Cascade in a Driven Quantum Gas

Abstract

We observe an inverse turbulent-wave cascade, from small to large lengthscales, in a driven homogeneous 2D Bose gas. Starting with an equilibrium condensate, we drive the gas isotropically on a lengthscale much smaller than its size, and observe a nonthermal population of modes with wavelengths larger than the drive one. At long drive times, the gas exhibits a steady nonthermal momentum distribution. At lengthscales increasing from the drive one to the system size, this distribution features in turn: (i) a power-law spectrum with an exponent close to the analytical result for a particle cascade in weak-wave turbulence, and (ii) a spectrum reminiscent of a nonthermal fixed point associated with universal coarsening in an isolated 2D gas. In further experiments, based on anisotropic driving, we reveal the complete qualitative picture of how the steady-state cascade forms.

Main text: 4 pages, 5 figures; Supplemental material: 1 page, 1 figure

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Cited by in corpus (8)

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• Simulating Quantum Turbulence with Matrix Product States
• Velocity correlations of vortices and rarefaction pulses in compressible planar quantum fluids
• Controlled generation of 3D vortices in driven atomic Josephson junctions
• Generation of wave turbulence in dipolar gases driven across their phase transitions