Sub-Molecular Probing of Light-Matter Interaction
Anna Rosławska, Université de Strasbourg, CNRS, IPCMS, UMR 7504, Strasbourg, France
Light-matter interaction plays a crucial role in the quantum properties of light emission from single molecules, and in electron-to-photon and photon-to-electron energy conversions. Recent works have shown that both the tunneling current of an STM and incoming laser radiation can be used to excite the intrinsic luminescence of individual molecules enabling light-matter interaction investigations with unprecedented resolution. In the talk, I will first discuss how STM-induced luminescence allows us to map the optical properties of single molecules with nearly atomic precision . With this approach, we are also able to mimic structures employed by photosynthetic systems and study sub-nm details of the energy transfer process using molecules as ancillary, passive or blocking elements to promote and direct resonant energy transfer between distant donor and acceptor units . Furthermore, using a tunable light source focused on the STM tip we drive and control the rate of a free-base phthalocyanine phototautomerization with sub-molecular precision (Fig. 1), providing a path to pilot the intrinsic reactivity of the molecule with an external controllable stimulus. We probe the excited states of the molecule, which drive the tautomerization, by recording tip-enhanced photoluminescence (TEPL) spectra and maps where varying patterns for non-resonant and resonant excitation conditions are observed . Such control over optical properties at the molecular level is possible only using this hyper-resolution optical approach, which does not suffer from ensemble averaging.
 Rosławska, A.; Neuman, T.; Doppagne, B.; Borisov. A. G.; Romeo, M.; Scheurer, F.; Aizpurua, J.; Schull, G., Phys. Rev. X 12, 011012, 2022.
 Cao, S.; Rosławska, A.; Doppagne, B.; Romeo, M; Feron, M.; Cherioux, F.; Bulou, H; Scheurer, F.; Schull, G., Nat. Chem., 13, 2021.
 Rosławska, A.; Kaiser K.; Romeo M.; Scheurer F.; Berciaud S.; Neuman T.; Schull G., submitted.
Fig. 1. Controlling phototautomerization with submolecular precision.