000106156 001__ 106156 000106156 005__ 20230519145400.0 000106156 0247_ $$2doi$$a10.1038/s41566-020-00731-5 000106156 0248_ $$2sideral$$a121334 000106156 037__ $$aART-2021-121334 000106156 041__ $$aeng 000106156 100__ $$aYoo, Daehan 000106156 245__ $$aUltrastrong plasmon–phonon coupling via epsilon-near-zero nanocavities 000106156 260__ $$c2021 000106156 5060_ $$aAccess copy available to the general public$$fUnrestricted 000106156 5203_ $$aVibrational ultrastrong coupling, where the light–matter coupling strength is comparable to the vibrational frequency of molecules, presents new opportunities to probe the interactions between molecules and zero-point fluctuations, harness cavity-modified chemical reactions and develop novel devices in the mid-infrared spectral range. Here we use epsilon-near-zero nanocavities filled with a model polar medium (SiO2) to demonstrate ultrastrong coupling between phonons and gap plasmons. We present classical and quantum-mechanical models to quantitatively describe the observed plasmon–phonon ultrastrong coupling phenomena and demonstrate a modal splitting of up to 50% of the resonant frequency (normalized coupling strength η > 0.25). Our wafer-scale nanocavity platform will enable a broad range of vibrational transitions to be harnessed for ultrastrong coupling applications 000106156 536__ $$9info:eu-repo/grantAgreement/ES/MINECO/MAT2017-88358-C3-1-R$$9info:eu-repo/grantAgreement/ES/MINECO/MAT2017-88358-C3-2-R 000106156 540__ $$9info:eu-repo/semantics/openAccess$$aAll rights reserved$$uhttp://www.europeana.eu/rights/rr-f/ 000106156 590__ $$a39.728$$b2021 000106156 591__ $$aPHYSICS, APPLIED$$b2 / 161 = 0.012$$c2021$$dQ1$$eT1 000106156 591__ $$aOPTICS$$b1 / 101 = 0.01$$c2021$$dQ1$$eT1 000106156 594__ $$a56.3$$b2021 000106156 592__ $$a10.991$$b2021 000106156 593__ $$aElectronic, Optical and Magnetic Materials$$c2021$$dQ1 000106156 593__ $$aAtomic and Molecular Physics, and Optics$$c2021$$dQ1 000106156 655_4 $$ainfo:eu-repo/semantics/article$$vinfo:eu-repo/semantics/acceptedVersion 000106156 700__ $$0(orcid)0000-0003-0381-3448$$aLeón Pérez, Fernando de 000106156 700__ $$aPelton, Matthew 000106156 700__ $$aLee, In-Ho 000106156 700__ $$aMohr, Daniel A. 000106156 700__ $$aRaschke, Markus B. 000106156 700__ $$aCaldwell, Joshua D. 000106156 700__ $$0(orcid)0000-0001-9273-8165$$aMartín-Moreno, Luis 000106156 700__ $$aOh, Sang-Hyun 000106156 7102_ $$12003$$2395$$aUniversidad de Zaragoza$$bDpto. Física Materia Condensa.$$cÁrea Física Materia Condensada 000106156 773__ $$g15 (2021), 125–130$$pNature Photonics$$tNature Photonics$$x1749-4885 000106156 8564_ $$s11686346$$uhttps://zaguan.unizar.es/record/106156/files/texto_completo.pdf$$yPostprint 000106156 8564_ $$s2925466$$uhttps://zaguan.unizar.es/record/106156/files/texto_completo.jpg?subformat=icon$$xicon$$yPostprint 000106156 909CO $$ooai:zaguan.unizar.es:106156$$particulos$$pdriver 000106156 951__ $$a2023-05-18-13:39:12 000106156 980__ $$aARTICLE