Lena Dogra and Maciej Galka (Cambridge) give a webinar on “Wave turbulence in homogeneous Bose gases: equation of state and universal dynamics.”

We will present our recent experimental results on wave turbulence in a homogeneous Bose gas; we characterise the properties of the non-thermal steady state and explore its formation under continuous drive.

To excite a wave turbulent cascade, we shake the gas strongly using a large-scale oscillating force. We observe that the far-from equilibrium cascade obeys an equation of state (EoS) in analogy to equilibrium thermodynamics, relating the cascade amplitude with the transported energy flux. By performing quenches between turbulent states, we find that this EoS holds irrespective of the starting conditions. The EoS for different (ground state) microscopic system parameters can be empirically scaled onto each other.

We will further present how such a non-thermal steady state emerges starting from an equilibrium system. We observe the two key ingredients in the formation of steady-state turbulence – the emergence (restoration) of statistical momentum-space isotropy under anisotropic forcing, and the spatiotemporal scaling of the spectrum of excitations at times before any energy is dissipated.