Anomalous Doppler Effect in Superfluid and Supersolid Atomic Gases
Year: 2025
Authors: Zawislak T., Indik MS., Stringari S., Recati A.
Autors Affiliation: Univ Trento, Pitaevskii BEC Ctr, CNR INO, Via Sommar 14, I-38123 Trento, Italy; Univ Trento, Dipartimento Fis, Via Sommar 14, I-38123 Trento, Italy; Univ Belgrade, Inst Phys Belgrade, Pregrev 118, Belgrade 11080, Serbia.
Abstract: By employing the formalism of hydrodynamics, we derive novel analytic predictions for the Doppler effect in superfluids with broken Galilean invariance and hosting persistent currents at zero temperature. We consider two scenarios: when Galilean invariance is broken explicitly (by external potentials) and spontaneously, as it happens in a supersolid. In the former case, the presence of a stationary current affects the propagation of sound via an anomalous Doppler term proportional to the density derivative of the superfluid fraction. In supersolids, where, according to Goldstone theorem, distinct sounds of hybrid superfluid and crystal nature can propagate, the Doppler effect can be very different for each sound. Quantitative estimates of the Doppler shifts are obtained for Bose-Einstein condensed atomic gases, described by Gross-Pitaevskii theory. The estimates are obtained both calculating the thermodynamic parameters entering the hydrodynamic results and from full time-dependent simulations.
Journal/Review: PHYSICAL REVIEW LETTERS
Volume: 134 (22) Pages from: 226001-1 to: 226001-7
More Information: We acknowledge useful discussions with Jean Dalibard, and William D. Phillips. Stimulating discussions with Giovanni Modugno and members of the Pisa Dysprosium Lab are also acknowledged. This work has been supported by the Provincia Autonoma di Trento, Q@TN (the joint lab between University of Trento, FBK-Fondazione Bruno Kessler, INFN-National Institute for Nuclear Physics, and CNR-National Research Council) , CINECA consortium through the award under the ISCRA initiative, for the availability of HPC resources. Part of the work was computed on Deeplearning cluster supported by the initiative Dipartimenti di Eccellenza 2018-2022 (Legge 232/2016) funded by the MUR. M. & Scaron;.acknowledges funding provided by the Institute of Physics Belgrade, through the grant by the Ministry of Science, Technological Development, and Innovations of the Republic of Serbia.r acknowledges funding provided by the Institute of Physics Belgrade, through the grant by the Ministry of Science, Technological Development, and Innovations of the Republic of Serbia.KeyWords: 4th Sound; Hydrodynamic Theory; Shift; PhaseDOI: 10.1103/PhysRevLett.134.226001
