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CANCELED - THz-ARPES band structure movies of Dirac surface currents

Asteartea, Irailak 01, 2020 - 12:00
Online seminar, Donostia International Physics Center
CANCELED - Ulrich Höfer, Philipps-Universität Marburg, Fachbereich Physik, Germany
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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 [1].

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.

[1] J. Reimann et al., Nature 562, 396 (2018).

Link to the seminar: https://dipc-org.zoom.us/j/92886910533