Electron vortex beams for chirality probing at the nanoscale

TL;DR

This paper introduces a novel method using electron vortex beams in electron microscopes to detect nanoscale electromagnetic chirality with high spatial resolution, leveraging the orbital angular momentum of modulated electron beams.

Contribution

It proposes a new approach for probing electromagnetic chirality at the nanoscale using coherent superpositions of electron vortex states, demonstrating sensitivity to chiral near fields.

Findings

Effective detection of chirality in nanostructures demonstrated

High spatial resolution achieved through electron vortex beam spectroscopy

Potential for nanoscale chiral characterization in materials science

Abstract

In this work we propose a method for probing the chirality of nanoscale electromagnetic near fields utilizing the properties of a coherent superposition of free-electron vortex states in electron microscopes. Electron beams optically modulated into vortices carry orbital angular momentum, thanks to which they are sensitive to the spatial phase distribution and topology of the investigated field. The sense of chirality of the studied specimen can be extracted from the spectra of the electron beam with nanoscale precision owing to the short picometer de Broglie wavelength of the electron beam. We present a detailed case study of the interaction of a coherent superposition of electron vortex states and the optical near field of a golden nanosphere illuminated by circularly polarized light as an example, and we examine the chirality sensitivity of electron vortex beams on intrinsically chiral plasmonic nanoantennae.