Superfluidity and sound propagation in disordered Bose gases

Superfluidity describes the ability of quantum matter to flow without friction. Due to its fundamental role in many transport phenomena, it is crucial to understand the robustness of superfluid properties to external perturbations. Here, we theoretically study the effects of speckle disorder on the...

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Bibliographic Details
Published in:arXiv.org 2024-07
Main Authors: Geier, Kevin T, Maki, Jeff, Biella, Alberto, Dalfovo, Franco, Giorgini, Stefano, Stringari, Sandro
Format: Article
Language:English
Subjects:
Bose-Einstein condensates
Compressibility
Coupled modes
Damping
Fluids
Perturbation theory
Propagation
Propagation modes
Sound propagation
Sound reproduction
Sound waves
Superfluidity
Transport phenomena
Wave propagation
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Summary:Superfluidity describes the ability of quantum matter to flow without friction. Due to its fundamental role in many transport phenomena, it is crucial to understand the robustness of superfluid properties to external perturbations. Here, we theoretically study the effects of speckle disorder on the propagation of sound waves in a two-dimensional Bose-Einstein condensate at zero temperature. We numerically solve the Gross-Pitaevskii equation in the presence of disorder and employ a superfluid hydrodynamic approach to elucidate the role of the compressibility and superfluid fraction on the propagation of sound. A key result is that disorder reduces the superfluid fraction and hence the speed of sound; it also introduces damping and mode coupling. In the limit of weak disorder, the predictions for the speed of sound and its damping rate are well reproduced by a quadratic perturbation theory. The hydrodynamic description is valid over a wide range of parameters, while discrepancies become evident if the disorder becomes too strong, the effect being more significant for disorder applied in only one spatial direction. Our predictions are well within the reach of state-of-the-art cold-atom experiments and carry over to more general disorder potentials.
ISSN:2331-8422