Superfluidity and sound propagation in disordered Bose gases

Year: 2025

Authors: Geier K.T., Maki J., Biella A., Dalfovo F., Giorgini S., Stringari S.

Autors Affiliation: Univ Trento, Pitaevskii BEC Ctr, CNR INO, I-38123 Trento, Italy; Univ Trento, Dipartimento Fis, I-38123 Trento, Italy; INFN, Trento Inst Fundamental Phys & Applicat, I-38123 Trento, Italy; Technol Innovat Inst, Quantum Res Ctr, POB 9639, Abu Dhabi, U Arab Emirates; Univ Konstanz, Dept Phys, D-78464 Constance, Germany.

Abstract: 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 in 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.

Journal/Review: PHYSICAL REVIEW RESEARCH

Volume: 7 (1)      Pages from: 13187-1  to: 13187-19

More Information: We thank G. Astrakharchik, J. Dalibard, J. Beugnon, S. Nascimbene, F. Rabec, P. Massignan, D. Perez-Cruz, and J. Spielman for useful discussions. K.T.G. would like to thank the College de France and the team of J. Dalibard at the Laboratoire Kastler Brossel for the kind hospitality. A.B. would li ke to thank the Institut Henri Poincare (UAR 839 CNRS-Sorbonne Universite) and the LabEx CARMIN (ANR-10-LABX-59-01) for their support. This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (Grant Agreement No. 804305) and by the European Union-NextGeneration EU, within PRIN 2022, PNRR M4C2, Project TANQU 2022FLSPAJ (CUP Grant No. B53D23005130006) . This work has benefited from Q@TN, the joint lab between the University of Trento, FBK-Fondazione Bruno Kessler, INFN-National Institute for Nuclear Physics, and CNR-National Research Council. We further acknowledge support by Provincia autonoma di Trento.
KeyWords: Anderson Localization; Mott-insulator; Transition; Phase; Glass
DOI: 10.1103/PhysRevResearch.7.013187