Photon Bubble Turbulence in Cold Atomic Gases [CL]

Turbulent radiation flow is ubiquitous in many physical systems where light-matter interaction becomes relevant. Photon bubbling, in particular, has been identified as the main source of turbulent radiation transport in many astrophysical objects, such as stars and accretion disks. This mechanism takes place when radiation trapping in optically dense media becomes unstable, leading to the energy dissipation from the larger to the smaller bubbles. Here, we report on the observation of photon bubble turbulence in cold atomic gases in the presence of multiple scattering of light. The instability is theoretically explained by a fluid description for the atom density coupled to a diffusive transport equation for the photons, which is known to be accurate in the multiple scattering regime investigated here. We determine the power spectrum of the atom density fluctuations, which displays an unusual $\sim k^{-4}$ scaling, and entails a complex underlying turbulent dynamics resulting from the formation of dynamical bubble-like structures. We derive a power spectrum from the theoretical photon bubble model which, to a high level of accuracy, explains the observations. The experimental results reported here, along with the theoretical model we developed may shed light on the analogue photon bubble instabilities in astrophysical scenarios.

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J. Rodrigues, J. Rodrigues, A. Ferreira, et. al.
Thu, 28 Apr 16

Comments: 5 pages