Generalized Gouy Rotation of Electron Vortex beams in uniform magnetic fields

TL;DR

This paper introduces a generalized Gouy rotation framework for electron vortex beams in magnetic fields, explaining experimental observations and predicting a broader range of rotation behaviors, including reversals, beyond traditional Landau state models.

Contribution

It develops a new theoretical model linking Gouy phase to vortex beam rotation, extending understanding of electron vortex dynamics in magnetic fields.

Findings

Good agreement with experimental data

Predicts broader angular frequency spectrum

Explains rotation reversal in vortex beams

Abstract

The intrinsic rotation of electron vortex beams, governed by their phase structure, has been experimentally observed in magnetic fields by breaking the beam's cylindrical symmetry. However, conventional Landau states, which predict three fixed angular frequencies, cannot fully account for the existing experimental observations. To address this limitation, we introduce and derive the generalized Gouy rotation angle, which links the Gouy phase of an extended Landau state -- featuring a periodically oscillating beam width -- to the experimentally observed angular variation. In particular, this framework predicts a broader spectrum of angular frequencies and captures the reversal of rotation direction observed in electron vortex beams with negative topological charge. Calculations based on experimental parameters show good agreement with previously published data and are further validated here by numerical simulations using the Chebyshev method. Our results are, in principle, applicable to any system involving electron vortex beams in uniform magnetic fields, and provide a foundation for exploring vortex electrons in Glaser and other nonuniform magnetic fields.