867. Wilhelm and Else Heraeus Seminar on "Quantum Electron-Photon Interactions"

Interaction of vortex electron beams with chiral particle arrays

Not scheduled

20m

Charles University (Prague)

Poster

Speaker

Marek Zálešák (Brno University of Technology, Central European Institute of Technology)

Description

Focused electron beams are ideal probes for investigating low-energy excitations, such as phonons or plasmons, at the nanoscale [1]. Combining scanning transmission electron microscopy (STEM) with spectroscopic techniques, such as electron energy-loss spectroscopy (EELS) and cathodoluminescence (CL), allows us to obtain nanometer spatial resolution combined with spectral resolution in the order of meV. Recently, it was suggested that performing EELS or CL with phase-tailored instead of phase-constant electron beams could yield further information on the optical near fields, such as their phase or emergence of chirality [2].
Here, we investigate the interaction between a special class of electron probes known as vortex electron beams (VEBs) [3,4] carrying orbital angular momentum (OAM), which can be transferred to the nanostructures or their optical near fields [2]. Specifically, we theoretically investigate the interaction between VEBs and either finite or infinite periodic arrays of nanospheres arranged in a helical configuration. We calculate the corresponding EELS and CL probabilities using a quantum-mechanical description of the electron beam and analyze the emergence of dichroism in the detected electron spectra. We further focus on the properties of the CL radiation with respect to the handedness of the vortex electron beam, the position of the center of the electron trajectory, and the OAM transfer. Also, we are interested in the influence of OAM transfer on light emission (polarization and radiation direction), which emerges as a generalization of the Smith-Purcell effect [5] to chiral structures. The presented theory provides insight into light manipulation at the nanoscale, the influence of chirality on the condition of electron phase matching, and the interaction of free electrons with chiral specimens.

[1] García de Abajo, F.J. et al., Rev. Mod. Phys., 82, 209-275 (2010)
[2] Asenjo-García, A. et al., Phys. Rev. Lett., 82, 066102 (2010)
[3] Verbeeck, J. et al., Nature, 467, 301–304 (2010).
[4] Tavabi, A. H. et al., App. Phys. Lett., 121, 073506 (2022)
[5] Smith, S. J., Purcell, E. M., Phys. Rev., 92, 1069 (1953)