Yoo, DaehanLeón-Pérez, Fernando dePelton, MatthewLee, In-HoMohr, Daniel A.Raschke, Markus B.Caldwell, Joshua D.Martín-Moreno, LuisOh, Sang-Hyun2021-01-262021-01-262020-12-07Yoo, D., de León-Pérez, F., Pelton, M. et al. Ultrastrong plasmon–phonon coupling via epsilon-near-zero nanocavities. Nat. Photonics (2020). https://doi.org/10.1038/s41566-020-00731-5https://doi.org/10.1038/s41566-020-00731-5http://hdl.handle.net/11603/20626Vibrational 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.9 pagesen-USThis item is likely protected under Title 17 of the U.S. Copyright Law. Unless on a Creative Commons license, for uses protected by Copyright Law, contact the copyright holder or the author.Text