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arXiv · 2506.18224

Space-time duality in polariton dynamics

Suheng Xu·Seunghwi Kim·Rocco A. Vitalone·Birui Yang·Josh Swann·Enrico M. Renzi·Yuchen Lin·Taketo Handa·X. -Y. Zhu·James Hone·Cory Dean·Andrea Cavalleri·M. M. Fogler·Andrew J. Millis·Andrea Alu·D. N. Basov
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Abstract

The spatial and temporal dynamics of wave propagation are intertwined. A common manifestation of this duality emerges in the spatial and temporal decay of waves as they propagate through a lossy medium. A complete description of the non-Hermitian wave dynamics in such a lossy system, capturing temporal and spatial decays, necessitates the use of complex-valued frequency and/or wavenumber Eigen-values. Here, we demonstrate that the propagation of polaritons - hybrid light-matter quasiparticles - can be broadly controlled in space and time by temporally shaping their photonic excitation. Using time-domain terahertz near-field nanoscopy, we study plasmon polaritons in bilayer graphene at sub-picosecond time scales. Suppressed spatial decay of polaritons is implemented by temporally engineering the excitation waveform. Polaritonic space-time metrology data agree with our dynamic model. Through the experimental realization and visualization of polaritonic space-time duality, we uncover the effects of the spatio-temporal engineering of wave dynamics; these are applicable to acoustic, photonic, plasmonic, and electronic systems.

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Suheng Xu, Seunghwi Kim, Rocco A. Vitalone, Birui Yang, Josh Swann, Enrico M. Renzi, Yuchen Lin, Taketo Handa, X. -Y. Zhu, James Hone, Cory Dean, Andrea Cavalleri, M. M. Fogler, Andrew J. Millis, Andrea Alu, D. N. Basov. 2025-06-17. Space-time duality in polariton dynamics. https://arxiv.org/abs/2506.18224

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