Inelastic Mach-Zehnder Interferometry with Free Electrons

TL;DR

This paper demonstrates a novel inelastic interferometric imaging technique using a scanning electron Mach-Zehnder interferometer to study electron-plasmon interactions at the nanoscale.

Contribution

It introduces a new interferometric method with free electrons in a transmission electron microscope for inelastic imaging of nanoscale optical modes.

Findings

Interference signals are pi out of phase for inelastic vs elastic scattering.

The technique is sensitive to phase of localized optical modes.

Provides a new platform for controlling electron momentum and studying electron-matter interactions.

Abstract

We use a novel scanning electron Mach-Zehnder interferometer constructed in a conventional transmission electron microscope to perform inelastic interferometric imaging with free electrons. An electron wave function is prepared in two paths that pass on opposite sides of a gold nanoparticle, where plasmons are excited before the paths are recombined to produce electron interference. We show that the measured spectra are consistent with theoretical predictions, specifically that the interference signal formed by inelastically scattered electrons is pi out of phase with respect to that formed by elastically scattered electrons. This technique is sensitive to the phase of localized optical modes because the interference signal amounts to a substantial fraction of the transmitted electrons. We thus argue that inelastic interferometric imaging with our scanning electron Mach-Zehnder interferometer provides a new platform for controlling the transverse momentum of a free electron and studying coherent electron-matter interactions at the nanoscale.