Vorticity and quantum turbulence in the merging of superfluid helium nanodroplets
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Authors
Escartín, José María
Ancilotto, Francesco
Barranco, Manuel
Pi, Martí
Journal Title
Physical Review B
ISSN
2469-9950
Publisher
American Physical Society (APS)
Volume
99
Issue
14
Number
140505
Language
en
Type
Article
This Version
VoR
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Escartín, J. M., Ancilotto, F., Barranco, M., & Pi, M. (2019). Vorticity and quantum turbulence in the merging of superfluid helium nanodroplets. Physical Review B, 99 (14. 140505)https://doi.org/10.1103/physrevb.99.140505
Abstract
We have studied the merging of two identical ⁴He droplets at zero temperature, caused by their van der Waals mutual attraction. During the early stages of the merging, density structures appear which closely match the experimental observations by Vicente et al. [J. Low Temp. Phys. 121, 627 (2000)]. When the droplets are merging, quantized vortex-antivortex ring pairs nucleate at the surface and annihilate inside the merged droplet producing a roton burst. We also observe the nucleation of quantized vortex-antivortex rings that wrap the droplet surface and remain localized on the surface until they eventually decay into short-wavelength surface waves. Analysis of the kinetic energy spectrum discloses the existence of a regime where turbulence caused by vortex interaction and annihilation is characterized by a Kolmogorov power law. This is followed by another regime where roton radiation—produced by vortex-antivortex annihilation—dominates, whose hallmark is a weak, turbulent surface dynamics. We suggest that similar processes might appear in superfluid helium droplets after they capture impurities or if they are produced by hydrodynamic instability of a liquid jet. Experiments on collisions between recently discovered self-bound Bose-Einstein condensates should display a similar phenomenology.
Sponsorship
EPSRC (EP/P034616/1)
Identifiers
External DOI: https://doi.org/10.1103/physrevb.99.140505
This record's URL: https://www.repository.cam.ac.uk/handle/1810/292055
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