Speaker
Description
Electrons move the world. They drive our electronic devices and every chemical reaction in nature. To understand and control electron motion, we have to catch it in the act—inside materials and at their interfaces. But electrons are hard to pin down for two opposite reasons: the mobile electrons at the Fermi level move at velocities of up to a few nm/fs, while the strongly bound electrons sit localized at core levels with binding energies of up to several keV. Filming both therefore demands femtosecond soft x-ray flashes that strip electrons from the material after a short-pulse excitation and capture them frame by frame.
Here, we report on our mission to record and direct electronic films in quantum materials and at functional interfaces. Our approach unites, in a single experiment, the full electronic structure dynamics in energy-momentum space, including spin, via time- and spin-resolved ARPES, with atomic-site-specific chemical and structural dynamics in real space via time-resolved XPS and XPD. We can thus follow electrons, spins, and atoms simultaneously, each on its own natural time scale. Crucially, these three are not independent; their dynamics are intertwined, and capturing them in one experiment lets us disentangle how they drive one another. By shaping the pump pulses—tuning their wavelength and wavefront—we move from observing to directing: this one-stop multimodal technique becomes a tool to discover and even create hidden and transient phases of quantum matter.
This talk surveys both the enabling technology and the scientific frontier it opens: watching, and steering, the electronic life of quantum matter at high-repetition-rate XFELs.
