Ultrafast Photocurrents in a topological insulator - an inside view
Max Planck Quantum Matter Seminar
- Date: Feb 17, 2022
- Time: 03:00 PM - 04:00 PM (Local Time Germany)
- Speaker: Hadas Soifer
- School of Physics and Astronomy, Tel Aviv University
- Location: online via Zoom
- Host: Umberto de Giovannini
Photocurrents in topological materials have been associated with topological properties of the electronic bands, such as the Berry connection. However, despite experimental demonstrations of photocurrent generation in topological materials, it has remained unclear what part the topology actually plays in the process, and what stems from other contributions. We use time- and angle-resolved photoemission spectroscopy (trARPES) to resolve photocurrents in the excited electronic states of a topological insulator . Furthermore, by analyzing the rise times of the population following the optical excitation, we gain a complete view of the occupied and unoccupied electronic states, and how they are coupled by the light. This enables us to determine that photocurrents are excited only via the resonant optical transitions coupling to spin-orbital textured states, but not exclusively by topological bands. Our work provides a microscopic understanding of how to control photocurrents in materials with spin-orbit coupling and broken inversion symmetry, and paves the way to control of currents in topological states.
 H. Soifer et al., Phys. Rev. Lett., 122, 167401 (2019).