High quality-factor terahertz phonon-polaritons in layered lead iodide
While hyperbolic phonon-polaritons in van der Waals materials such as h-BN and α-MoO<sub>3</sub> have driven major advances in mid-infrared (IR) nanophotonics, further progress at longer THz wavelengths has been hampered due to material limitations and experimental challenges. Here, we report the discovery of long-lived hyperbolic phonon-polaritons in the deep THz range in layered PbI<sub>2</sub>. Using room-temperature scattering-type scanning near-field optical microscopy, we achieved real-space imaging and broadband spectral analysis of PbI<sub>2</sub> 2D crystals transferred onto different substrates with high near-field amplitude contrast and good agreement with theoretical models. Our measurements revealed an experimental figure-of-merit related to the propagating efficiency of the polaritons above 15-on par with state-of-the-art mid-IR benchmarks-and extreme field confinement of 264 for a 144 nm-thick flake, which can exceed 300 in slightly thinner samples. These findings demonstrate that PbI<sub>2</sub> combines strong anisotropy, low losses, and extreme mode confinement, making it a compelling candidate for deep-THz nanophotonic applications.
Authors
- Flávio H. Feres (ORCID: https://orcid.org/0000-0001-9812-974X)
- Adrian Cernescu (ORCID: https://orcid.org/0009-0002-7775-5017)
- Sophie Eliet (ORCID: https://orcid.org/0000-0001-8289-1473)
- Romain Peretti (ORCID: https://orcid.org/0000-0002-1707-7341)
- Théo Hannotte (ORCID: https://orcid.org/0000-0002-5516-4497)
- M. Faucher
- Cristiane Nascimento Santos
- Benjamin Walter (ORCID: https://orcid.org/0000-0002-3177-9059)
- Vanwolleghem Mathias
- Raul O. Freitas
- Jean-François Lampin
Institutions
- Université Claude Bernard Lyon 1 (FR)
- École Centrale de Lyon (FR)
- Centre National de la Recherche Scientifique (FR)
- Université de Lille (FR)
- Institut des Nanotechnologies de Lyon (FR)
- Brazilian Synchrotron Light Laboratory (BR)
- Institut d'Electronique, de Microélectronique et de Nanotechnologie (FR)
- Attocube Systems (Germany) (DE)
- Brazilian Center for Research in Energy and Materials (BR)
- Onco Lille (FR)
- Institut National des Sciences Appliquées de Lyon (FR)
- Université Polytechnique Hauts-de-France (FR)
Publication Details
- Journal
- Nature Communications
- Published
- 2026-02-04
- DOI
- https://doi.org/10.1038/s41467-026-69027-6
- Primary Topic
- Plasmonic and Surface Plasmon Research
- Type
- article
- Field-Weighted Citation Impact
- 0.00
Funders
- Agence Nationale de la Recherche
- Fundação de Amparo à Pesquisa do Estado de São Paulo
- Conselho Nacional de Desenvolvimento Científico e Tecnológico