Space-time duality in polariton dynamics
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.
Cite
@article{arxiv.2506.18224,
title = {Space-time duality in polariton dynamics},
author = {Suheng Xu and Seunghwi Kim and Rocco A. Vitalone and Birui Yang and Josh Swann and Enrico M. Renzi and Yuchen Lin and Taketo Handa and X. -Y. Zhu and James Hone and Cory Dean and Andrea Cavalleri and M. M. Fogler and Andrew J. Millis and Andrea Alu and D. N. Basov},
journal= {arXiv preprint arXiv:2506.18224},
year = {2025}
}