Vortex nucleation induced phonon radiation from a moving electron bubble in superfluid 4He

We construct an efficient zero-temperature semilocal density functional to dynamically simulate an electron bubble passing through superfluid He-4 under various pressures and electric fields up to nanosecond time scale. 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.