Würzburg ToCoTronics Colloquium

Exploration of essential photophysical phenomena at the level of individual quantum objects requires highly specialized optical spectroscopies. These techniques require working at the very limit of instrument sensitivity or the use of plasmonic nanostructures - in order to overcome the fundamental resolution limits achievable with visible and infrared light. The recent developments emerging in the field of Scanning Probe Light Microscopy bring the unique opportunity to pursue intriguing, often hard-to-access interactions between light and matter at submolecular scale, with the finesse characteristic for the method based on atomically-sharp tips. The plasmonic nanocavity formed naturally between the tip and sample enables massive enhancement of the light field coupling to the studied objects, and therefore visualization of the fascinating photophysics within nanoscopic emitters. The modes of operation can be switched between the electroluminescence, photoluminescence and tip-enhanced Raman spectroscopies. The addition of the toolbox of cryogenic STM, STS and AFM provides a reliable support in questions of the system geometry and electronic configuration.1 As the emitted photons and their spectra carry a rich information about the eigenmodes, charges, vibronics and temporal evolution of the transient states, we can build a detailed picture of the cycles comprising the process of single-photon generation, tracing the relevant energy conversion pathways,2 quasiparticle delocalization over excitonic nanoclusters,3 interaction with electrical fields and vibronic coupling to electronic transitions.4

Figure - Example of the capability of the Scanning Probe Light Microscopy - observation and control of electroluminescence emission patterns of delocalized excitations on molecular aggregates, created from PTCDA.

References
[1] Charge carrier injection electroluminescence with CO functionalized tips on single molecular emitters. J Doležal, P Merino, J Redondo, L Ondič, A Cahlík and M Švec, Nano Lett. 19, 8605-861 (2019)
[2] Exciton-Trion Conversion Dynamics in a Single Molecule. J Doležal, S Canola, P Merino and M Švec, ACS Nano 15, 7694–7699 (2021)
[3] Real space visualization of entangled excitonic states in charged molecular assemblies. J Doležal, S Canola, P Hapala, R. Ferreira, P Merino and M Švec, ACS Nano 16, 1082-1088 (2022)
[4] Evidence of trion-libron coupling in chirally adsorbed single molecules. J Doležal, S Canola, P Hapala, RCC Ferreira, P Merino, M Švec, Nature Comm. 13, 6008 (2022)