Probing Mie-resonant nanoparticles with swift electron beams

We discuss the richness of information that one can extract about the optical response of Mie-resonant high-index dielectric nanoparticles, when excited by a swift electron beam, in electron-energy loss or cathodoluminescence spectroscopy measurements. In particular, we analyse how, apart from Mie modes of electric or magnetic multipolar type, electron beams passing nearby or through the particle can produce a diversity of resonant or interference spectral features, due to the interaction of Mie modes with transition or Cherenkov radiation, or with intrinsic material processes such as interband transitions. We thus highlight the importance of precise analytic or semi-analytic theoretical approaches for the interpretation of measured or simulated spectra.