SKM 2023 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 48: Ultra-fast Phenomena
HL 48.8: Talk
Friday, March 31, 2023, 11:30–11:45, POT 251
Intermolecular conical intersections in acceptor-donor-acceptor aggregated molecules — •Somayeh Souri1, Katrin Winte1, Antonietta De Sio1, Christoph Lienau1, Elena Mena-Osteritz3, Peter Bäuerle2, Teresa Kraus3, Fulu Zheng2, Mohamed Madjet2, and Sergei Tretiak4 — 1University of Oldenburg, Germany — 2University of Bremen, Germany — 3Ulm University, Germany — 4Los Alamos National Laboratory, USA
In molecules, strong coupling between electronic excitations and vibrational modes may result in conical intersections (CoIns) of multidimensional potential energy surfaces. At CoIns different electronic states cross and couple strongly via vibrational modes. This results in large nonadiabatic couplings violating the Born-Oppenheimer approximation. While CoIns are ubiquitous in molecules, not much is known about their occurrence and relevance for intermolecular ultrafast energy and charge transfer dynamics in the solid state. Here, we reveal the existence of intermolecular CoIns in thin films of aggregated acceptor-donor-acceptor-type oligomers by ultrafast two-dimensional electronic spectroscopy (2DES). The 2DES maps show a grid-like peak pattern at early times, followed by a rapid reduction of the peak spacings which transforms into a featureless map after only ~40 fs. We take this abrupt change in the 2DES maps as clear evidence for the passage of the optically launched vibrational wave packet through the intermolecular CoIn in the thin films. Our results, which are confirmed by simulations, suggest new opportunities for guiding the coherent flow of energy and charge in solid-state nanostructures.