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Interplay of Kelvin-Helmholtz and superradiant instabilities of an array of quantized vortices in a two-dimensional Bose-Einstein condensate
by Luca Giacomelli, Iacopo Carusotto
This Submission thread is now published as
Submission summary
| Authors (as registered SciPost users): | Iacopo Carusotto · Luca Giacomelli |
| Submission information | |
|---|---|
| Preprint Link: | https://arxiv.org/abs/2110.10588v5 (pdf) |
| Date accepted: | 2022-09-07 |
| Date submitted: | 2022-07-22 11:44 |
| Submitted by: | Giacomelli, Luca |
| Submitted to: | SciPost Physics |
| Ontological classification | |
|---|---|
| Academic field: | Physics |
| Specialties: |
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| Approach: | Theoretical |
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 nature 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.
Author comments upon resubmission
thank you for handling our submission and for giving our work the possibility of further consideration from a third referee.
We thank the referees for the careful reading of our work. We responded directly to their reports and took into account their comments by making minor modifications to the manuscript. We added some references that were pointed out and added some comments to clarify the points that were raised. We attached to our responses the new manuscript with the changes highlighted in red.
For what concerns the first point raised in Report 2 we tried our best to get to a common point with the referee whose point of view is however quite different from ours: on one hand, they would like a detailed study of the applicability of the hydrodynamic theory; on the other hand, our aim is not to apply the hydrodynamic theory but to directly use the microscopic theory that best describes our system. We also think that the main new results in our work are in the following of the article, where we do not mention the hydrodynamic theory any longer. We hence think that a detailed study of the regime in which the hydrodynamic theory holds would fall outside the scope of the present article. As such, this problem is best addressed in a future independent work.
We think that with these new additions our article is even clearer and we hope that it can now be accepted for publication in SciPost Physics.
Best regards,
The authors
List of changes
- In the introduction we added a comment of the work mentioned by the first referee in their first point
- In section 3 we changed the notation in equation (7) and in the following equations to address the potential confusion that the second referee pointed out
- In the caption of Figure 2 and in the following discussion we corrected the previous statement that said that negative energy modes start to be present at $\Delta v=2c_s$. We added more details on the fact that the general picture we give there does not capture the full physics of the system, that is fully explored in the following sections.
- In Section 4.1 we added a couple of sentences to make clearer that we are not applying the hydrodynamic theory to our system and that we are not using it to benchmark our results.
- In Section 4.2.1, following the comment of the first referee, we moved a paragraph that was not well placed to footnote 5 earlier in the text.
- in Section 4.3 we updated our comment on the precession of vortices in trapped condensates, including the new reference suggested by the first referee.
Published as SciPost Phys. 14, 025 (2023)