Robust Surface-Induced Enhancement of Exciton Transport in Magic-Angle-Oriented Molecular Aggregates

TL;DR

This paper demonstrates that exciton transport in magic-angle molecular aggregates can be significantly enhanced near metallic surfaces due to light-matter interactions, with potential for controlled exciton dynamics through environment engineering.

Contribution

The study combines macroscopic quantum electrodynamics simulations and analytical models to reveal the robust enhancement of exciton diffusion near metallic surfaces, elucidating the underlying near-field coupling mechanisms.

Findings

Significant enhancement of exciton diffusion coefficient near silver surfaces.

Robustness of enhancement across various parameters like separation and frequency.

Differences in diffusion scaling near metallic surfaces compared to free space.

Abstract

Exciton transport in molecular aggregates with magic-angle orientation is expected to be strongly suppressed due to their negligible dipole-dipole interactions. However, recent reports show that light-matter interactions can significantly enhance exciton transport attributed to the effective long-range coupling mediated by the photonic fields. To elucidate their interplay, we employ the macroscopic quantum electrodynamics framework to simulate exciton transport within a chromophore array arranged in a magic-angle configuration in proximity to a silver surface. Our results show a significant enhancement of the exciton diffusion coefficient that is robust across variations in chromophore-surface separation, intermolecular distance, and molecular transition frequency. Furthermore, based on the image-dipole method, we derive analytical expressions that agree well with numerical simulations, revealing the enhancement's origin in the near-field coupling term as induced by the radiative scattering at the metallic surface. More importantly, we observe non-trivial differences in the diffusion coefficient's scaling near metallic surfaces compared to free space. Our findings highlight the potential to control exciton transport by designing coupled exciton-photon systems and engineering the dielectric environments.