Inelastic Scattering of Electron Beams by Nonreciprocal Nanotructures

Abstract

Probing optical excitations with high resolution is important for understanding their dynamics and controlling their interaction with other photonic elements. This can be done using state-of-the-art electron microscopes, which provide the means to sample optical excitations with combined meV--sub-nm energy--space resolution. For reciprocal photonic systems, electrons traveling in opposite directions produce identical signals, while this symmetry is broken in nonreciprocal structures. Here, we theoretically investigate this phenomenon by analyzing electron energy-loss spectroscopy (EELS) and cathodoluminescence (CL) in structures consisting of magnetically biased InAs as an instance of gyrotropic nonreciprocal material. We find that the spectral features associated with excitations of InAs films depend on the electron propagation direction in both EELS and CL, and can be tuned by varying the applied magnetic field within a relatively modest sub-tesla regime. The magnetic field modifies the optical field distribution of the sampled resonances, and this in turn produces a direction-dependent coupling to the electron. The present results pave the way to the use of electron microscope spectroscopies to explore the near-field characteristics of nonreciprocal systems with high spatial resolution.

arXiv comment7 pages, 6 figures, 52 references

References in corpus (16)

• Topological Photonics
• Possible Realization of Directional Optical Waveguides in Photonic Crystals with Broken Time-Reversal Symmetry
• Optical excitations in electron microscopy
• Electron Beam Spectroscopy for Nanophotonics
• Inverse-designed photonic circuits for fully passive, bias-free Kerr-based nonreciprocal transmission and routing
• Giant tunable nonreciprocity of light in Weyl semimetals
• Position and momentum mapping of vibrations in graphene nanostructures in the electron microscope
• Surface plasmon polaritons in topological Weyl semimetals
• Optical Excitations with Electron Beams: Challenges and Opportunities
• Generation of Traveling Surface Plasmon Waves by Free-Electron Impact
• Can Copper Nanostructures Sustain High-Quality Plasmons?
• Tailored nanoscale plasmon-enhanced vibrational electron spectroscopy
• Giant Interatomic Energy-Transport Amplification with Nonreciprocal Photonic Topological Insulators
• Electron energy loss and induced photon emission in photonic crystals
• Asymmetric Cherenkov Emission in a Topological Plasmonic Waveguide
• Nonreciprocal guided waves in presence of swift electron beams