Theory of momentum-resolved phonon spectroscopy in the electron microscope

TL;DR

This paper develops a theoretical framework combining first principles calculations with experimental data to interpret momentum-resolved phonon spectra obtained via electron microscopy, enabling nanoscale phonon analysis.

Contribution

It introduces a comprehensive theoretical approach for predicting and interpreting momentum-dependent phonon spectra in electron microscopes, integrating lattice dynamics with experimental validation.

Findings

Theoretical predictions match experimental measurements on boron nitride.

Method enables interpretation of phonon spectra at nanometer resolution.

Framework facilitates analysis of momentum-resolved phonon data.

Abstract

We provide a theoretical framework for the prediction and interpretation of momentum dependent phonon spectra due to coherent inelastic scattering of electrons. We complete the approach with first principles lattice dynamics using periodic density functional theory and compare to recent electron energy loss measurements on cubic and hexagonal boron nitride performed within a scanning transmission electron microscope (STEM). The combination of theory and experiment provides the ability to interpret momentum dependent phonon spectra obtained at nanometer spatial resolution in the electron microscope.