Who: CANCELED - Ulrich Höfer, Philipps-Universität Marburg, Fachbereich Physik, Germany
Place: Online seminar, Donostia International Physics Center
Date: Tuesday, 1 September 2020, 12:00
Time-resolved photoelectron spectroscopy combines femtosecond pump-probe techniques with angle-resolved photoelectron spectroscopy (ARPES). New opportunities for this powerful technique arise in combination with THz excitation. As an example, I will explain how THz-ARPES can be used to measure electron transport in the Dirac surface state of a three-dimensional topological insulator in a contact-free fashion and with femtosecond time-resolution. We induce electrical currents in these states with strong THz transients and directly access their dynamics in momentum space with subcycle time resolution. As a result of spin-momentum locking, the accelerated spin-polarized electrons reach ballistic mean free paths of several hundreds of nanometers. Topological insulators are thus promising materials for future lightwave-driven electronics .
Future applications of subcycle THz-ARPES are expected to benefit from the availability of high laser harmonics lab sources for photoemission or from combined THz + UV beamlines at synchrotrons or FELs. THz-ARPES of adsorbed molecules at surfaces should, e.g., make it possible to perform orbital tomography during chemical reactions.
 J. Reimann et al., Nature 562, 396 (2018).
Link to the seminar: https://dipc-org.zoom.us/j/92886910533