Dynamics of fine particles due to quantized vortices on the surface of superfluid $^4$He

TL;DR

This study investigates the irregular motions of electrically charged fine particles on superfluid helium's surface, attributing these behaviors to interactions with quantized vortices supported by vortex filament model calculations.

Contribution

It provides the first support for vortex-particle interactions causing observed particle motions using vortex filament model simulations.

Findings

Particles exhibit circular and quasi-linear motions.

Vortex filament model supports vortex-particle interaction hypothesis.

Vortices influence particle dynamics on superfluid helium surface.

Abstract

Peculiar dynamics of a free surface of the superfluid 4He has been observed experimentally with a newly established technique utilizing a number of electrically charged fine metal particles trapped electrically at the surface by Moroshkin et al. They have reported that some portion of the particles exhibit some irregular motions and suggested the existence of quantized vortices interacting with the metal particles. We have conducted calculations with the vortex filament model, which turns out to support the idea of the vortex-particle interactions. The observed anomalous metal particle motions are roughly categorized into two types; (1) circular motions with specific frequencies, and (2) quasi-linear oscillations. The former ones seem to be explained once we consider a vertical vortex filament whose edges are terminated at the bottom and at a particle trapped at the surface. Although it is not yet clear whether all the anomalous motions are due to the quantum vortices, the vortices seem to play important roles for the motions.