Theory of modern spectroscopic methods at nanometer scale

Project title: Theory of modern spectroscopic methods at nanometer scale
Main applicant: Jan Rusz, Division of Materials Theory
Grant amount: 3 640 000 SEK for the period 2022-2025

Transmission electron microscopy (TEM) is a powerful tool in modern material research and nano-technology. Since the development of aberration correctors around the turn of the millennium, the electron microscopes access structural and chemical information down to atomic scale. Recent instrumental developments in TEM include 1) direct electron detectors, which significantly improve the noise characteristics over the standard CMOS detectors, 2) magnetic-field-free lens, simultaneously allowing to maintain the atomic spatial resolution, and 3) new generation of electron beam monochromators allowing to reach an energy resolution of 4 meV. New improved hardware gives TEM access to spectroscopy of atomic vibrations and detection of relatively weak magnetic signals, among others.

We will address the challenges for theory to explain and reliably interpret the novel measurements and describe new ways of probing matter. Recently we have proposed a new simulation method for describing vibrational electron energy loss spectroscopy (EELS) utilizing non-equilibrium molecular dynamics calculations. Our method scales linearly with number of atoms in the structure model and thus allows to treat systems with interfaces and/or defects. We will mature the method for routine applications. Further, we propose a conceptually similar method for unprecedented magnon EELS utilizing atomistic spin dynamics. We will develop methods for studying buried magnetic layers using electron magnetic circular dichroism.