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

Area of Science:

• Quantum physics
• Condensed matter physics
• Nonlinear dynamics

Background:

• Bose-Einstein condensates are quantum fluids with unique properties.
• Turbulence in quantum systems can exhibit exotic phenomena like inverse cascades.
• Understanding energy transfer in driven quantum systems is crucial.

Purpose of the Study:

• To investigate the phenomenon of inverse turbulent-wave cascade in a driven homogeneous 2D Bose gas.
• To characterize the nonthermal momentum distribution formed during the cascade.
• To elucidate the formation mechanism of the steady-state cascade under anisotropic driving.

Main Methods:

• Experimental setup involving a driven homogeneous 2D Bose gas.
• Isotropic and anisotropic driving protocols applied to the condensate.
• Measurement of momentum distribution to analyze energy transfer and spectral properties.

Main Results:

• Observation of an inverse cascade transferring energy from small to large length scales.
• Formation of a steady nonthermal momentum distribution with distinct spectral features.
• Identification of a power-law spectrum related to weak-wave turbulence and a spectrum linked to universal coarsening.
• Qualitative picture of steady-state cascade formation revealed through anisotropic driving.

Conclusions:

• The study demonstrates an inverse turbulent-wave cascade in a driven 2D Bose gas.
• The observed nonthermal momentum distribution exhibits characteristics of both weak-wave turbulence and universal coarsening.
• Anisotropic driving experiments provide a comprehensive understanding of steady-state cascade formation in quantum systems.