Freiburg 2024 – scientific programme

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MO: Fachverband Molekülphysik

MO 24: Poster: Experimental Techniques

MO 24.4: Poster

Thursday, March 14, 2024, 17:00–19:00, Tent C

Near field spectroscopy of molecular aggregates with topological phases — •Sidhartha Nayak, Aritra Mishra, and Alexander Eisfeld — Max Planck Institute for the Physics of Complex Systems, Dresden, Germany

In this theoretical study, we focus on delocalized electronic excitonic states in molecular aggregates, particularly those exhibiting topological phases. It has been shown that a two-dimensional molecular aggregate, composed of two different sublattices and complex transition dipole moments, possesses topological edge states [1]. However, these states are predominantly ’dark’ in traditional far-field absorption spectra. We consider a typical scattering scanning optical near-field microscopy (s-SNOM) setup, where the aggregate interacts with the near field stemming from a metallic tip [2, 3]. With the help of s-SNOM, we can not only excite these dark states but also record spatially resolved absorption spectra, revealing clear signatures of both excitonic edge states and bulk 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] S. Nayak, F. Zheng and A. Eisfeld, J. Chem. Phys.   155, 134701 (2021)

Keywords: Molecular aggregates; Excitons; Scanning near field optical microscopy; Edge states; Topology