On Small Beams with Large Topological Charge II: Photons, Electrons and Gravitational Waves

TL;DR

This paper demonstrates that large topological charge beams exhibit similar spatial structure modifications across photons, electrons, and gravitational waves, due to different physical mechanisms, indicating a universal phenomenon for various elementary particles.

Contribution

It reveals that the spatial structure change with large topological charge is a universal effect for different particles, explained by distinct physical reasons for each species.

Findings

Spatial structure changes in photons, electrons, and gravitational waves with large topological charge.

Different physical mechanisms cause the structure modification: electromagnetic field components, spin-orbit coupling, and space-time curvature.

Potential for similar effects in composite particles and neutrinos.

Abstract

Beams of light with a large topological charge significantly change their spatial structure when they are focused strongly. Physically, it can be explained by an emerging electromagnetic field component in the direction of propagation, which is neglected in the simplified scalar wave picture in optics. Here we ask: Is this a specific photonic behavior, or can similar phenomena also be predicted for other species of particles? We show that the same modification of the spatial structure exists for relativistic electrons as well as for focused gravitational waves. However, this is for different physical reasons: For electrons, which are described by the Dirac equation, the spatial structure changes due to a Spin-Orbit coupling in the relativistic regime. In gravitational waves described with linearized general relativity, the curvature of space-time between the transverse and propagation direction leads to the modification of the spatial structure. Thus, this universal phenomenon exists for both massive and massless elementary particles with Spin 1/2, 1 and 2. It would be very interesting whether other types of particles such as composite systems (neutrons or C$_{60}$) or neutrinos show a similar behaviour and how this phenomenon can be explained in a unified physical way.