Year: 2026
Type: preprint
Abstract: Collective molecular excitations govern energy transport in light-harvesting and optoelectronic materials. Theory predicts that excitonic band topology can generate edge-confined states, offering a route to direct energy flow in molecular systems, yet experimental evidence is lacking. Here we use scanning tunnelling microscopy-induced luminescence to image Frenkel excitons in two-dimensional zinc phthalocyanine molecular crystals with nanometer resolution. By varying cluster size, we observe the transition from discrete quantum-confined excitations to collective excitonic bands and directly resolve their real-space wavefunctions. We identify an excitonic state localized at the crystal perimeter and show, through comparison with microscopic theory, that it originates from the momentum-resolved non-trivial topology of the bulk excitonic bands. Our results establish molecular crystals as a platform for engineering topological excitonic states and provide a strategy for controlling energy transport through excitonic band engineering.
Source: arXiv (Cornell University)
Institutions: Centre National de la Recherche Scientifique, Institut de Physique et Chimie des Matériaux de Strasbourg, Université de Strasbourg, Czech Academy of Sciences, FZU - Institute of Physics of the Czech Academy of Sciences, University of Göttingen, Ikerbasque, Donostia International Physics Center
Language: English
Subfield: Condensed Matter Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7220995366