Oral: Electron Energy Loss Spectroscopy with Structured Probes

Advances in monochromation and aberration-correction in electron microscopy have made electron energy loss spectroscopy (EELS) a widely used tool in materials science. EELS has been used to map surface plasmons, phonon excitations, and even magnons. Typically, samples are excited using a focused probe or large planewave illumination. We study how electron beams can be structured with various techniques such as diffracting holograms [1,2] or programmable phaseplates [3]. Structuring the electron wavefunction allows the beam to be tailored to the symmetries of the sample. This can be used to probe specific excitations or transfer orbital angular momentum (OAM) [4]. We discuss the techniques required for these experiments as well as the theoretical and experimental work that has been done in this exciting area of electron microscopy.

1. M Uchida and A Tonomura, Nature 464 (2010), p. 737. https://doi.org/10.1038/nature08904

2. B McMorran et al., Science 332 (2011), p. 192. https://doi.org/10.1126/science.1198804

3. J Verbeeck et al., Ultramicroscopy 190 (2018), p. 58. https://doi.org/10.1016/j.ultramic.2018.03.017

4. Guzzinati et al., Nature Communications 8 (2017), 14999. https://doi.org/10.1038/ncomms14999