Elastic scattering of vortex electrons provides direct access to the Coulomb phase

TL;DR

This paper proposes a novel method using elastic scattering of vortex electron beams to directly measure the Coulomb phase, a fundamental quantum phase shift affecting charged particle interactions, which was previously unobservable experimentally.

Contribution

It introduces a new experimental approach with vortex electrons to access the Coulomb phase through interference effects in elastic scattering.

Findings

Demonstrates that vortex electron scattering can reveal the Coulomb phase.

Shows that azimuthal asymmetry in scattering encodes the Coulomb phase.

Provides a theoretical framework for measuring the Coulomb phase experimentally.

Abstract

Vortex electron beams are freely propagating electron waves carrying adjustable orbital angular momentum with respect to the propagation direction. Such beams were experimentally realized just a few years ago and are now used to probe various electromagnetic processes. So far, these experiments used the single vortex electron beams, either propagating in external fields or impacting a target. Here, we investigate the elastic scattering of two such aligned vortex electron beams and demonstrate that this process allows one to experimentally measure features which are impossible to detect in the usual plane-wave scattering. The scattering amplitude of this process is well approximated by two plane-wave scattering amplitudes with different momentum transfers, which interfere and give direct experimental access to the Coulomb phase. This phase (shift) affects the scattering of all charged particles and has thus received significant theoretical attention but was never probed experimentally. We show that a properly defined azimuthal asymmetry, which has no counterpart in plane-wave scattering, allows one to directly measure the Coulomb phase as function of the scattering angle.