Energetics and Possible Formation and Decay Mechanisms of Vortices in Helium Nanodroplets

Abstract

The energy and angular momentum of both straight and curved vortex states of a helium nanodroplet are examined as a function of droplet size. For droplets in the size range of many experiments, it is found that during the pickup of heavy solutes, a significant fraction of events deposit sufficient energy and angular momentum to form a straight vortex line. Curved vortex lines exist down to nearly zero angular momentum and energy, and thus could in principle form in almost any collision. Further, the coalescence of smaller droplets during the cooling by expansion could also deposit sufficient angular momentum to form vortex lines. Despite their high energy, most vortices are predicted to be stable at the final temperature (0.38 K) of helium nanodroplets due to lack of decay channels that conserve both energy and angular momentum.

arXiv comment10 pages, 8 figures, RevTex 4, submitted to Phys. Rev. B

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• Vortex arrays in nanoscopic superfluid helium droplets
• Absorption spectrum of Ca atoms attached to ${}^4$He nanodroplets
• Evaporative Cooling of Helium Nanodroplets with Angular Momentum Conservation
• Shapes of rotating normal fluid 3He versus superfluid 4He droplets in molecular beams
• Vortex arrays in a rotating superfluid He-4 nanocylinder
• Quantized vortices in ${}^4$He droplets: a quantum Monte Carlo study
• Merging of superfluid Helium nanodroplets with vortices