Antonietta De Sio, Ephraim Sommer, Xuan Trung Nguyen, Lynn Groß, Duško Popović, Benjamin Tyler Nebgen, Sebastian Fernandez-Alberti, Stefano Pittalis, Carlo Andrea Rozzi, Elisa Molinari, Elena Mena-Osteritz, Peter Bäuerle, Thomas Frauenheim, Sergei Tretiak & Christoph Lienau
Nat. Nanotechnol. (2020).
Conical intersections (CoIns) of multidimensional potential energy surfaces are ubiquitous in nature and control pathways and yields of many photo-initiated intramolecular processes. Such topologies can be potentially involved in the energy transport in aggregated molecules or polymers but are yet to be uncovered. Here, using ultrafast two-dimensional electronic spectroscopy (2DES), we reveal the existence of intermolecular CoIns in molecular aggregates relevant for photovoltaics. Ultrafast, sub-10-fs 2DES tracks the coherent motion of a vibrational wave packet on an optically bright state and its abrupt transition into a dark state via a CoIn after only 40 fs. Non-adiabatic dynamics simulations identify an intermolecular CoIn as the source of these unusual dynamics. Our results indicate that intermolecular CoIns may effectively steer energy pathways in functional nanostructures for optoelectronics.
Intermolecular conical intersections in molecular aggregates