Cross-sections of Andreev scattering by quantized vortex rings in 3He-B

TL;DR

This paper numerically investigates how quantized vortex rings in superfluid 3He-B scatter thermal quasiparticles via Andreev reflection, analyzing dependence on size, orientation, and screening effects.

Contribution

It introduces a numerical analysis of Andreev scattering cross-sections for vortex rings, including orientation averaging and screening effects, advancing understanding of quasiparticle-vortex interactions.

Findings

Cross-section depends on vortex ring size and orientation.

Screening effects increase as vortex rings decrease in size.

Orientation-averaged cross-section is relevant for experiments.

Abstract

We studied numerically the Andreev scattering cross-sections of three-dimensional isolated quantized vortex rings in superfluid 3He-B at ultra-low temperatures. We calculated the dependence of the cross-section on the ring's size and on the angle between the beam of incident thermal quasiparticle excitations and the direction of the ring's motion. We also introduced, and investigated numerically, the cross-section averaged over all possible orientations of the vortex ring; such a cross-section may be particularly relevant for the analysis of experimental data. We also analyzed the role of screening effects for Andreev reflection of quasiparticles by systems of vortex rings. Using the results obtained for isolated rings we found that the screening factor for a system of unlinked rings depends strongly on the average radius of the vortex ring, and that the screening effects increase with decreasing the rings' size.