Vortex Nucleation Induced Phonon Radiation from a Moving Electron Bubble in Superfluid 4He

TL;DR

This paper develops a semi-local density functional to simulate electron bubbles in superfluid 4He, revealing how vortex nucleation and phonon radiation contribute to energy dissipation at high speeds.

Contribution

It introduces an efficient simulation method for electron bubbles in superfluid helium, capturing vortex nucleation, vortex-ring shedding, and phonon radiation dynamics.

Findings

High-speed bubbles cause surface vibrations and vortex shedding.

Phonon radiation dissipates more energy than vortex rings.

Simulation results align with experimental drift velocities at low pressures.

Abstract

We construct an efficient zero-temperature semi-local density functional to dynamically simulate an electron bubble passing through superfluid 4He under various pressures and electric fields up to nanosecond timescale. Our simulated drift velocity can be quantitatively compared to experiments particularly when pressure approaches zero. We find that the high-speed bubble experiences remarkable expansion and deformation before vortex nucleation occurs. Accompanied by vortex-ring shedding, drastic surface vibration is generated leading to intense phonon radiation into the liquid. The amount of energy dissipated by these phonons is found to be greater than the amount carried away solely by the vortex rings. These results may enrich our understanding about the vortex nucleation induced energy dissipation in this fascinating system.