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O: Fachverband Oberflächenphysik

O 79: Ultrafast Electron Dynamics III

O 79.3: Vortrag

Donnerstag, 20. März 2025, 11:00–11:15, H2

Exciton wave function signatures from time-resolved photoemission tomography of an organic molecular layer — •Siegfried Kaidisch¹, Marcel Theilen², Monja Stettner³, Eric Fackelman³, Galit Cohen⁴, Amir Kleiner⁴, Christian Simon Kern¹, Andreas Windischbacher¹, Sivan Refaely-Abramson⁴, Frank Stefan Tautz³, Ulrich Höfer², and Peter Puschnig¹ — ¹Institute of Physics, University of Graz, Austria — ²Fachbereich Physik, Philipps-Universität Marburg — ³PGI-3, FZ Jülich & RWTH Aachen University — ⁴Weizmann Institute of Science, Israel

Oriented layers of organic molecules adsorbed on passivated metal surfaces are a promising class of interfaces for studying electron dynamics at femtosecond timescales. In particular, time-resolved photoemission tomography promises to reveal information about the electron distribution in optically excited states. Using the example of sexithiophene (6T) multilayers adsorbed on Cu(110)-p(2x1)O, we observe photoemission patterns for the low-energy excited states. These measured momentum maps exhibit signatures that cannot be explained by a mere population of the lowest unoccupied molecular orbital of 6T. To analyze the source of these features, we perform GW/BSE (Bethe-Salpeter equation) calculations on multiple levels of theory (gas-phase, cluster, embedded and periodic calculations). Using the framework of photoemission orbital tomography for excited states, we also simulate the photoemission patterns and thereby shed light on the nature of the exciton wave function of the lowest optically allowed state.

Keywords: Many-body perturbation theory; Excitons; Photoemission orbital tomography; Organic molecular layers