Electronic structure of a persistent excitonic fluid far beyond the Mott limit
Abstract
Excitons are conventionally expected to destabilize at high photoexcitation densities, as screening weakens the electron-hole attraction. Recent studies, however, challenge this paradigm, suggesting that excitons generated by strong optical pumping can remain stable even beyond the onset of population inversion. Here, using time- and angle-resolved photoelectron spectroscopy on 2D hybrid perovskites, we provide direct evidence for such a high-density excitonic state, characterized by a distinctive Mexican-hat dispersion. Remarkably, this excitonic band reconstruction endures for orders of magnitude longer than the optical coherence time, revealing a population-sustained electronic structure that survives well into the incoherent regime. The excitonic resonance also persists far beyond optical saturation, at densities where exciton wavefunctions strongly overlap. Our findings reveal a long-lived, high-density quantum fluid of excitons with characteristics reminiscent of a BCS condensate, an electronic structure markedly different from that of the dilute limit.
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BibTeX
@misc{qi2026electronic,
title = {{Electronic structure of a persistent excitonic fluid far beyond the Mott limit}},
author = {Weiyan Qi and Stefano Ponzoni and Ashim Pramanik and Vitaly Gorelov and Yannis Laplace and Gianluca Stefanucci and Enrico Perfetto and Esteban Morcos and Marino Marsi and Steven Francis Udaundo and Sebastian Maherlein and Amina Taleb-Ibrahimi and Kaibo Zheng and Tonu Pullerits and Luca Perfetti},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.32437},
eprint = {2610.32437},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.32437},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Electronic structure of a persistent excitonic fluid far beyond the Mott limit
AU - Weiyan Qi
AU - Stefano Ponzoni
AU - Ashim Pramanik
AU - Vitaly Gorelov
AU - Yannis Laplace
AU - Gianluca Stefanucci
AU - Enrico Perfetto
AU - Esteban Morcos
AU - Marino Marsi
AU - Steven Francis Udaundo
AU - Sebastian Maherlein
AU - Amina Taleb-Ibrahimi
AU - Kaibo Zheng
AU - Tonu Pullerits
AU - Luca Perfetti
PY - 2026
DA - 2026/10/23
PB - arXiv
DO - 10.48550/arxiv.2610.32437
UR - https://arxiv.org/abs/2610.32437
AB - Excitons are conventionally expected to destabilize at high photoexcitation densities, as screening weakens the electron-hole attraction. Recent studies, however, challenge this paradigm, suggesting that excitons generated by strong optical pumping can remain stable even beyond the onset of population inversion. Here, using time- and angle-resolved photoelectron spectroscopy on 2D hybrid perovskites, we provide direct evidence for such a high-density excitonic state, characterized by a distinctive Mexican-hat dispersion. Remarkably, this excitonic band reconstruction endures for orders of magnitude longer than the optical coherence time, revealing a population-sustained electronic structure that survives well into the incoherent regime. The excitonic resonance also persists far beyond optical saturation, at densities where exciton wavefunctions strongly overlap. Our findings reveal a long-lived, high-density quantum fluid of excitons with characteristics reminiscent of a BCS condensate, an electronic structure markedly different from that of the dilute limit.
ER -