Quantum Electron Wavepacket Spectroscopy

ongoing

Can we shape an electron wavepacket in space and time? Can we tailor it to probe material properties that are currently inaccessible? Recent work has shown that high-energy electrons (80-200 keV) interacting with strong light fields can absorb or release quantized energy packets equal to the photon energy. This dresses the electron into a superposition state composed of a spectrum of energy-loss and -gain sidebands. Here we exploit this Photon-Induced Near-field Electron Microscopy (PINEM) effect in order to create a revolutionary new method of tailoring the spatial and temporal distribution of electron wavepackets at will. Building on my strong expertise in the field of electron-light-matter interactions and nanophotonics, we will incorporate the PINEM effect into a scanning electron microscope (SEM) and integrate it with advanced cathodoluminescence (CL) light detection. Using 5 keV electrons and advanced optical metamaterial designs we will amplify the PINEM effect by a factor 1000. Using spatial light modulation we spatially vary the PINEM light fields which results in wide control over the electron energy spectrum. We create electron-metasurface interactions that stretch, chirp, or split the electron wavepacket, enabling entirely new ultrafast pump-probe detection schemes of optical excitations and relaxations. Using a compact solid-state implementation we perform subsequent PINEM operations on a single electron and perform a full quantum state reconstruction of the electron’s density matrix that represents the interaction. We derive the wavepacket amplitude and phase and reveal dephasing processes in optical excitations. The new PINEM-SEM-CL technique opens up an entirely new world of electron microscopy applications in integrated optics, nanophotonics, and opto-electronics and will provide detailed insights into fundamental electron-light-matter interactions that have been inaccessible thus far.