Sequential Interaction of Low-Energy Electrons with Nanostructured Samples for Quantum-Sensitive Measurements

• Applicants: Professor Dr. Peter Hommelhoff; Professorin Nahid Talebi, Ph.D.
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas ; Experimental Condensed Matter Physics
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 525347396

Exploring the interactions between electron beams and optical near-fields in electron microscopes has recently been transformed into schemes for advanced characterization of light-matter interactions. Spontaneous interactions of electron beams with the optical near-fields have routinely been employed in two spectroscopy scenarios, namely cathodoluminescence and electron energy-loss spectroscopy. On the stimulated interaction side, electron energy-gain spectroscopy (or photon-induced near-field electron microscopy) have also been intensively studied. Particularly, various fundamental concepts, such as entanglement between photons and electrons, strong-coupling effects, interferometry, and shaping the phase and amplitude of electron wavepackets have recently been explored. However, all the investigations stated above are routinely employed in transmission electron microscopes with electron kinetic energies around 100 keV. In contrast, slow electron dynamics and their interactions with light and samples are less explored. Particularly in the range below 30 keV, fascinating physics with important applications are expected, since the routinely employed adiabatic approximations could break down, due to the sensitivity of slow electrons to the electromagnetic interactions. This is exactly the energy range offered by a variety of less-expensive and easier-to-handle scanning electron microscopes with a large sample chamber, allowing for simple integration of a variety of detectors, analyzers, electron optics, and manipulators in close proximity of the sample. The large chamber provided by scanning electron microscopes sets the stage for advanced interferometry, sequential, and multi-interaction experiments of the electron beam with optical near-field distributions, which are the main subjects of the present proposal. The sequential photons generated by the interaction of the electron wavepacket with two interaction points are here superimposed to explore the mutual coherence, or even entanglement, between the spontaneously-generated photons. On the stimulated interaction side, the interaction of electron wavepackets with laser-induced near-field excitations will be explored for advanced interferometry and unravelling Rabi physics for slow electron wavepackets. The present proposal hence provides the basis for self-interferometry of slow-electron wavepackets with multiple interaction points, to both explore quantum-path interferences as well as decoherence phenomena in the interaction of electron wavepackets with light and nanostructures. Particularly, we aim at design, realization, and characterization of structures for enhanced electron-photon interactions, within both spontaneous and stimulated interaction mechanisms, in order to enhance the light-generation yield for advanced electron-driven photon sources, but also for electron-beam shaping and generation of attosecond electron pulse trains.

• DFG Programme: Research Grants
• International Connection: Israel
• International Co-Applicant: Professor Dr. Roy Shiloh