Topological Frenkel excitons in 2D molecular crystals
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.
Related
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BibTeX
@misc{stein2026topological,
title = {{Topological Frenkel excitons in 2D molecular crystals}},
author = {Quentin Stein and Sidhartha Nayak and Song Jiang and Jakob Kuhlke and Michelangelo Romeo and Thomas Frederiksen and Fabrice Scheurer and Katharina Kaiser and Tomas Neuman and Guillaume Schull},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.09149},
eprint = {2610.09149},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.09149},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Topological Frenkel excitons in 2D molecular crystals
AU - Quentin Stein
AU - Sidhartha Nayak
AU - Song Jiang
AU - Jakob Kuhlke
AU - Michelangelo Romeo
AU - Thomas Frederiksen
AU - Fabrice Scheurer
AU - Katharina Kaiser
AU - Tomas Neuman
AU - Guillaume Schull
PY - 2026
DA - 2026/10/06
PB - arXiv
DO - 10.48550/arxiv.2610.09149
UR - https://arxiv.org/abs/2610.09149
AB - 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.
ER -