Electron vortex beams: an in-depth theoretical study
24 March 2016
UAntwerp, Campus Drie Eiken, Promotiezaal Q0.02 - Universiteitsplein 1 - 2610 Antwerpen-Wilrijk
Ruben Van Boxem
Jo Verbeeck & Bart Partoens
PhD defence Ruben Van Boxem - Faculty of Science, Department of Physics
An electron microscope, much like the usual light microscope, can be used to magnify objects. Using electrons, atoms can be imaged, and atomic scale properties can be measured directly. This works by focusing an electron beam to a spot smaller than an atom. This work is about shaping that spot into a special doughnut shape, by transforming the electron beam into a vortex beam. These electron vortex beams are a fundamental quantum state that exhibit unique properties such as orbital angular momentum, which influence the way these electrons interact with matter.
Through the additional rotational momentum, it is expected these beams can light up properties such as magnetic fields and allow for an atomic scale resolution image of these properties. Some of the first, fundamental theoretical steps were treated in this thesis, including how a vortex electron scatters on an atom, and how it channels through a crystal at high speed (and what this teaches us about the material under observation). Aside from providing solid insight into the mechanics of these systems, the (semi-)analytical approach presented in this work allows for a bottoms-up approach to guide future experimental design. This hopefully leads to improved electron microscopy techniques using electron vortex transformations in the near future.