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Vorticity and quantum turbulence in the merging of superfluid helium nanodroplets

Published version
Peer-reviewed

Type

Article

Change log

Authors

Escartín, José María 
Ancilotto, Francesco 
Barranco, Manuel 
Pi, Martí 

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.

Description

Keywords

cond-mat.mes-hall, cond-mat.mes-hall, cond-mat.quant-gas

Journal Title

Physical Review B

Conference Name

Journal ISSN

2469-9950
2469-9969

Volume Title

99

Publisher

American Physical Society (APS)

Rights

All rights reserved
Sponsorship
Engineering and Physical Sciences Research Council (EP/P034616/1)