Excitonic Coupling Suppresses Phonon-Induced Polariton Group Velocity Renormalization
Abstract
Exciton-polaritons can transport electronic excitation energy ballistically over distances far exceeding those accessible to bare excitons, yet their measured group velocities are often substantially lower than those predicted from the bare polariton dispersion. Recent experiments have shown that excitonic transfer coupling of the materials coupled inside the cavity can reduce the magnitude of group velocity renormalization, even though it does not impact the measured optical dispersion relation of polaritons. We derive an analytical, finite-temperature theory for the phonon-renormalized lower polariton group velocity that explicitly considers the impact of exciton transfer coupling. Our theory suggests that phonon-mediated virtual scattering of polariton states into dark states and back makes the magnitude of the group velocity renormalization sensitive to the dark exciton dispersion at large momentum. We use mixed quantum–classical dynamics simulations to corroborate the analytical predictions, capture experimental trends in layered halide perovskites, and show that stronger excitonic coupling helps preserve the ballistic character of polariton propagation. These results identify the excitonic transfer integral as a molecular design variable for preserving fast, coherent polariton transport under strong light–matter coupling.
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BibTeX
@misc{montillaortega2026excitonic,
title = {{Excitonic Coupling Suppresses Phonon-Induced Polariton Group Velocity Renormalization}},
author = {Alejandro Montilla-Ortega and Santanu Poddar and Milan Delor and Pengfei Huo},
howpublished = {ChemRxiv},
year = {2026},
month = oct,
doi = {10.26434/chemrxiv.15009944/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15009944/v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Excitonic Coupling Suppresses Phonon-Induced Polariton Group Velocity Renormalization
AU - Alejandro Montilla-Ortega
AU - Santanu Poddar
AU - Milan Delor
AU - Pengfei Huo
PY - 2026
DA - 2026/10/05
PB - ChemRxiv
DO - 10.26434/chemrxiv.15009944/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15009944/v1
AB - Exciton-polaritons can transport electronic excitation energy ballistically over distances far exceeding those accessible to bare excitons, yet their measured group velocities are often substantially lower than those predicted from the bare polariton dispersion. Recent experiments have shown that excitonic transfer coupling of the materials coupled inside the cavity can reduce the magnitude of group velocity renormalization, even though it does not impact the measured optical dispersion relation of polaritons. We derive an analytical, finite-temperature theory for the phonon-renormalized lower polariton group velocity that explicitly considers the impact of exciton transfer coupling. Our theory suggests that phonon-mediated virtual scattering of polariton states into dark states and back makes the magnitude of the group velocity renormalization sensitive to the dark exciton dispersion at large momentum. We use mixed quantum–classical dynamics simulations to corroborate the analytical predictions, capture experimental trends in layered halide perovskites, and show that stronger excitonic coupling helps preserve the ballistic character of polariton propagation. These results identify the excitonic transfer integral as a molecular design variable for preserving fast, coherent polariton transport under strong light–matter coupling.
ER -