Exotic self-trapped states of an electron in superfluid helium

TL;DR

This paper investigates the possibility that exotic negative ions in superfluid helium are electrons bound to vortex structures, proposing that these states are smaller and different from known electron bubbles.

Contribution

It introduces a theoretical model suggesting electrons can bind to vortex rings in superfluid helium, explaining exotic ion states observed experimentally.

Findings

Electron pressure insufficient to cavitate helium and form bubbles

Estimated vortex ring radius (~0.7 nm) smaller than electron bubbles

Exotic ions may be electrons bound to complex vortex structures

Abstract

We explore the possibility that the fast and exotic negative ions in superfluid helium are electrons bound to quantized vortex structures, the simplest being a ring. In the states we consider, the electron energy is only slightly below the conduction band minimum of bulk helium. To support our proposal we present two calculations. In the first, we show that the electron pressure on the vortex core is insufficient to cavitate the helium and form an electron bubble. In the second, we estimate the equilibrium radius of the vortex ring that would bind an electron and find it is much smaller than the electron bubble, about 0.7 nm. The many exotic ions reported in experiments might be bound states of an electron with more complex vortex structures.