Speaker
Description
Recent advances in ultrafast science and electron microscopy are enabling unprecedented control over free electrons across a wide range of energies, spatial scales, and interaction regimes. By combining strong optical fields, nanoscale structures, and tailored electron wavepackets, it is becoming possible to probe and manipulate electron motion on its natural attosecond timescale while exploring new quantum phenomena. Here, we present three studies that investigate complementary aspects of light-electron and electron-nanostructure interactions, spanning attosecond tunneling and transport dynamics, electron-induced electron emission, and phase-matched control of low-energy electrons.
In the first study, we integrate a conventional scanning tunneling microscope (STM) with an ultrafast femtosecond laser to achieve electron microscopy with extreme spatial and temporal resolution. We demonstrate attosecond control of the electric current in the nanoscale STM tunneling junction using the waveform of the laser field. Based on good agreement of the experiment with several theory calculations, we estimate an electron burst duration of 860 as. Our study shows that the STM junction consisting of nanotip, nanogap and conductive sample shows unique ultrafast physics compared to photoemission from a freestanding nanotip into vacuum.
In the second study, we theoretically investigate the interaction of a fast electron beam from a transmission electron microscope (TEM) with a freestanding metallic nanotip. In an aloof geometry where the electron beam is passing the apex of the nanotip at a distance of 1-3 nm, we predict the emission of low-energy electrons, both directly by the localized “white light” field of the fast TEM electron and by the optical near-field that it induces at the apex. An experimental realization of this scenario will be a first step towards interaction of a shaped electron wavepacket with a quantum system and will also be sensitive to the particle-wave duality of the TEM electron.
The third study investigates the interaction of low-energy electrons (20-200eV) with a phase-matched light field. Our analytical and one-dimensional numerical study shows that slow electrons are subject to strong confinement in the energy domain due to the nonvanishing curvature of the electron dispersion. The spectral trap is tunable and an appropriate choice of light field parameters can reduce the interaction dynamics to only two energy states. The capacity to trap electrons expands the scope of electron beam physics, free-electron quantum optics and quantum simulators.