Ultrastrong Plasmon–Phonon Coupling Enabled by Acoustic Graphene Plasmons

Lee, In-Ho ; de León-Pérez, Fernando (Universidad de Zaragoza) ; Yoo, Daehan ; Ryu, Eui-Hyoun ; Low, Tony ; Caldwell, Joshua D. ; Martín-Moreno, Luis ; Oh, Sang-Hyun

Resumen: Vibrational ultrastrong coupling (USC) opens new opportunities for controlling chemical reactivity and advancing mid-infrared nanophotonics. Here, we demonstrate USC in an ultrathin polar dielectric using acoustic graphene plasmons (AGPs). Unlike conventional graphene plasmons, whose coupling weakens with a reduced dielectric thickness, AGPs maintain strong coupling through enhanced field confinement in narrow dielectric gaps. This enables strong coupling in a polar film as thin as λ/8,000 and USC at λ/2,000. While USC is usually attributed to transverse optical phonons, we identify interface phonon polaritons at polar–nonpolar boundaries as an additional contributor. By tuning the AGP coupling to both phonon types, we observe a transition from a single anticrossing to two distinct anticrossings. This platform, sustaining USC in an extremely small volume, provides a promising basis for mid-infrared nanophotonics and quantum optics.

Idioma: Inglés

DOI: 10.1021/acs.nanolett.5c04495

Año: 2025

Publicado en: Nano Letters 25, 51 (2025), 17650-17658
ISSN: 1530-6984

Financiación: info:eu-repo/grantAgreement/ES/MCIU/PID2023-148359NB-C21
Financiación: info:eu-repo/grantAgreement/ES/MICINN-AEI/PID2020-115221GB-C41
Financiación: info:eu-repo/grantAgreement/ES/MICIU CEX2023-001286-S

Tipo y forma: Artículo (Versión definitiva)

Área (Departamento): Área Física Materia Condensada (Dpto. Física Materia Condensa.)