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arXiv · 2609.37142

Second-order coherence properties of ultrafast polariton dynamics in plasmonic lattices

Evgeny A. Mamonov·Lukas Freter·Sioneh Eyvazi·Elliot W. Lloyd·Päivi Törmä
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Abstract

The first-order coherence properties of strongly coupled systems supporting polariton lasing and Bose-Einstein condensation (BEC) have been thoroughly studied and show consistent results. In contrast, second-order coherence properties have been found to vary for different systems, and the second-order coherence function can deviate from the value of one, typical for atomic BEC, revealing super-Poissonian fluctuations even above the BEC/polariton lasing threshold. This calls for a deeper understanding of the emission statistics and dynamics in light-based condensates, especially in the non-equilibrium regime. Here we demonstrate a coherent state of polariton emission from a plasmonic lattice measured as the second-order coherence function value separately for $\mathrmΓ$- and non-$\mathrmΓ$-point radiation (ground state and high-energy tail). We observe a high degree of coherence with the value $g^{(2)}(τ=0)-1<10^{-4}$. We also demonstrate the ultrafast ($>$1 THz) nature of the dynamics. The process can be interpreted as a BEC with ultrafast, sub-50-fs thermalization, but we also suggest an alternative explanation as superradiance in a system where the emitters have vibrational degrees of freedom.

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Evgeny A. Mamonov, Lukas Freter, Sioneh Eyvazi, Elliot W. Lloyd, Päivi Törmä. 2026-09-29. Second-order coherence properties of ultrafast polariton dynamics in plasmonic lattices. https://arxiv.org/abs/2609.37142

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