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arXiv · 2607.16718

Measuring momentum-resolved dissipation of phonon-polaritons in LiNbO$_3$ with terahertz driving

Megan F. Biggs·Rossella Acampora·Niccolò Sellati·Mattia Udina·Lara Benfatto·Elsa Abreu·Steven L. Johnson·Jeremy A. Johnson
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Abstract

Mapping the dispersion of polaritons, hybrid quasiparticles arising from light-matter coupling, can provide key insights into the material dielectric response, coupling strength, and energy transfer pathways with other excitations. In this work, we present THz pump-Raman probe (TP-RP) as a versatile method for mapping the polariton dispersion in polar non-centrosymmetric materials, demonstrated here for the case of phonon-polaritons in LiNbO$_3$. By resonantly driving polaritonic modes with a broadband THz pump and probing them with a tunable NIR Raman pulse, TP-RP allows for the extraction of the momentum-dependence of both their frequency and damping rate with high accuracy. The spectral features observed in the pump-probe signal, including the polaritonic response as well as pulse artifacts, are reproduced within a many-body theoretical approach. Applying the technique to study the E(TO$_1$) phonon of LiNbO$_3$ enables the combined analysis of theory and experiments to uncover a nontrivial frequency dependence of the phonon intrinsic damping rate, revealing possible anharmonic couplings to other modes.

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Megan F. Biggs, Rossella Acampora, Niccolò Sellati, Mattia Udina, Lara Benfatto, Elsa Abreu, Steven L. Johnson, Jeremy A. Johnson. 2026-07-18. Measuring momentum-resolved dissipation of phonon-polaritons in LiNbO$_3$ with terahertz driving. https://arxiv.org/abs/2607.16718

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