Interplay of Kelvin-Helmholtz and superradiant instabilities of an array of quantized vortices in a two-dimensional Bose-Einstein condensate

Year: 2023

Authors: Giacomelli L., Carusotto I.

Autors Affiliation: Univ Trento, INO CNR BEC Ctr & Dipartimento Fis, Via Sommar 14, I-38050 Trento, Italy.

Abstract: We investigate the various physical mechanisms that underlie the dynamical instability of a quantized vortex array at the interface between two counter-propagating superflows in a two-dimensional Bose-Einstein condensate. Instabilities of markedly different na -ture are found to dominate in different flow velocity regimes. For moderate velocities where the two flows are subsonic, the vortex lattice displays a quantized version of the hydrodynamic Kelvin-Helmholtz instability (KHI), with the vortices rolling up and co-rotating. For supersonic flow velocities, the oscillation involved in the KHI can resonantly couple to acoustic excitations propagating away in the bulk fluid on both sides. This makes the KHI rate to be effectively suppressed and other mechanisms to dominate: For finite and relatively small systems along the transverse direction, the instability involves a repeated superradiant scattering of sound waves off the vortex lattice; for transversally unbound systems, a radiative instability dominates, leading to the simultaneous growth of a localized wave along the vortex lattice and of acoustic excitations propagating away in the bulk. Finally, for slow velocities, where the KHI rate is intrinsically slow, another instability associated to the rigid lateral displacement of the vortex lattice due to the vicinity of the system’s boundary is found to dominate.

Journal/Review: SCIPOST PHYSICS

Volume: 14 (2)      Pages from: 25-1  to: 25-23

More Information: We acknowledge financial support from the H2020-FETFLAG-2018-2020 project PhoQuS (n.820392) and from the Provincia Autonoma di Trento. LG thanks Giulia Piccitto for compu- tational help.
KeyWords: Shear-layer Instability; States
DOI: 10.21468/SciPostPhys.14.2.025

Citations: 3
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