SAMOP 2023 – scientific programme

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MO: Fachverband Molekülphysik

MO 5: Electronic Spectroscopy

MO 5.8: Talk

Tuesday, March 7, 2023, 12:45–13:00, F142

Near-field scanning optical microscopy of topologically protected excitons in molecular aggregates — •Sidhartha Nayak, Christopher W. Wächtler, and Alexander Eisfeld — MPIPKS, Dresden, Germany

Delocalized excitonic eignestates of molecular aggregates are responsible for the energy transfer from an incoming radiation into the aggregate. Static disorder, which can arise from an imperfect environment of each molecule, reduces the exciton transport and large disorders can even localize the exciton. It has been shown theoretically that a two-dimensional periodic array of tilted and interacting molecules in a homogeneous magnetic field shows topologically protected edge states [1] which are robust under local disorder. With a scattering scanning near-field optical microscope setup, one can not only record position dependent absorption spectra [2] but also reconstruct the wavefunctions from these specta [3]. In this contribution we study theoretically the near field spectra of the aforementioned 2D aggregates in which the molecules experience a disordered environment because of the probing metallic tip. Due to the topological protection, the edge states are robust even in the presence of the metallic nanoparticle, such that the recorded spectrum shows clear signatures of these edge states.

[1] J. Y. Zhou, S. K. Saikin, N. Y. Yao and A. Aspuru-Guzik, Nature materials 13, 1026-1032 (2014)

[2] X. Gao and A. Eisfeld, J. Phys. Chem. Lett.  9, 6003 (2018)

[3] F. Zheng, X. Gao and A. Eisfeld, Phys. Rev. Lett.  123, 163202 (2019)