Year: 2026
Type: preprint
Abstract: In molecular crystals, molecular excitations can hybridize into collective Frenkel excitons. Here we show that doubly degenerate excitations in planar two-dimensional molecular crystals generate excitonic bands with nontrivial momentum-resolved topological characteristics and edge states appearing only for selected crystallographic terminations. Using a model inspired by aggregates of zinc phthalocyanine molecules deposited on insulating surfaces, we demonstrate that the existence of edge excitons depends sensitively on the crystallographic orientation of the boundary and is governed by the Zak phase of the underlying bulk bands. The resulting edge states exhibit momentum-locked elliptical polarization textures originating from the internal structure of the molecular excitations, potentially enabling directional optical coupling and excitation transport. Our results establish a route toward topological and polarization-textured excitonic states in two-dimensional molecular materials.
Source: arXiv (Cornell University)
Institutions: Czech Academy of Sciences, FZU - Institute of Physics of the Czech Academy of Sciences, Centre National de la Recherche Scientifique, Institut de Physique et Chimie des Matériaux de Strasbourg, Université de Strasbourg, 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
Funders: European Commission, Agence Nationale de la Recherche, Institut National de la Santé et de la Recherche Médicale, Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, Université de Strasbourg, Akademie Věd České Republiky, Centre National de la Recherche Scientifique, Agencia Estatal de Investigación
OpenAlex ID: W7220929187