Orbital-resolved imaging of coherent femtosecond exciton dynamics in coupled molecules

TL;DR

This paper demonstrates orbital-resolved imaging of ultrafast coherent exciton dynamics in single molecules and coupled dimers, revealing coherence times and the influence of intermolecular interactions using ultrafast interferometry.

Contribution

It introduces a method for orbital-resolved imaging of exciton dynamics in molecules and dimers, providing new insights into coherence times and exciton control at the atomic scale.

Findings

Ultrafast exciton coherence time of ~70 fs in single molecules

Decreased coherence times for triplet excitons in coupled molecules

Atomic-scale imaging and control of excitons via photon-induced tunneling

Abstract

Optical excitation and control of excitonic wavepackets in organic molecules is the basis to energy conversion processes. To gain insights into such processes, it is essential to establish the relationship between the coherence timescales of excitons with the electronic inhomogeneity in the molecules, as well as the influence of intermolecular interactions on exciton dynamics. Here, we demonstrate orbital-resolved imaging of optically induced coherent exciton dynamics in single copper napthalocyanine (CuNc) molecules, and selective coherent excitation of dark and bright triplet excitons in coupled molecular dimers. Ultrafast photon-induced tunneling current enabled atomic-scale imaging and control of the excitons in resonantly excited molecules by employing excitonic wavepacket interferometry. Our results reveal an ultrafast exciton coherence time of ~ 70 fs in a single molecule, which decreases for the triplet excitons in interacting molecules.