Electron beam driven collective self hybridized exciton polaritons

@misc{darman2026electron,
  title = {{Electron beam driven collective self hybridized exciton polaritons}},
  author = {Parsa Darman and Maximilian Black and Prabhdeep Singh and Masoud Taleb and Victor DeManuel-Gonzalez and Sara Darbari and Fatemeh Chahshouri and Nahid Talebi},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.07164},
  eprint = {2609.07164},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.07164},
  note = {CC BY 4.0},
}

TY  - UNPB
TI  - Electron beam driven collective self hybridized exciton polaritons
AU  - Parsa Darman
AU  - Maximilian Black
AU  - Prabhdeep Singh
AU  - Masoud Taleb
AU  - Victor DeManuel-Gonzalez
AU  - Sara Darbari
AU  - Fatemeh Chahshouri
AU  - Nahid Talebi
PY  - 2026
DA  - 2026/09/25
PB  - arXiv
DO  - 10.48550/arxiv.2609.07164
UR  - https://arxiv.org/abs/2609.07164
AB  - Self-hybridized exciton polaritons in layered semiconductors emerge from the hybridization of excitonic resonances with confined photonic modes in films and provide a versatile platform for controlling light--matter interactions at the nanoscale. Yet, the nature of exciton--photon interactions and the collective and synchronous strong coupling of multiple excitons to the same photonic mode remain largely unexplored. Here, we use complementary momentum-resolved photoluminescence and cathodoluminescence spectroscopy to compare self-hybridized exciton polaritons in Ruddlesden--Popper perovskite flakes under optical and electron-beam excitation. We find that cathodoluminescence exhibits remarkably larger polaritonic level repulsion than photoluminescence, revealing an enhanced effective coupling strength under electron-beam excitation. We attribute this enhancement to the collective coherent excitation of multiple excitons by fast electrons, which couple to the same photonic mode and increase the interaction strength according to a g_N=g_1√N scaling, with an effective number of up to N≈23 coherently coupled excitonic oscillators. By reducing the electron kinetic energy, we further uncover a crossover to a partially incoherent excitation regime in which higher-order Fabry--Pérot exciton-polariton resonances disappear, leaving only the lowest polariton branches while coherent transition radiation persists. This transition arises because low-energy electrons excite excitons over extended spatial volumes, washing out the phase coherence required to sustain collective coupling and form polaritonic resonances. Our work shows that electron beams can actively modify collective light--matter coupling in layered semiconductors and establishes cathodoluminescence as a route to access excitation regimes beyond all-optical excitation schemes.
ER  -