Ultrastrong plasmon–phonon coupling via epsilon-near-zero nanocavities


Vibrational 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.

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Fig. 1: Wafer-scale resonant ENZ nanocavity platform for USC.
Fig. 2: Normal mode splittings due to ultrastrong plasmon–phonon coupling.
Fig. 3: Dispersion mapping and validation of theoretical model.

Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding authors upon reasonable request.


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We thank T. W. Ebbesen for helpful comments. This research was supported by grants from the US National Science Foundation (ECCS 1809240 to D.Y., D.A.M., S.-H.O.; ECCS 1809723 to I.-H.L., S.-H.O.) and the Samsung Global Research Outreach (GRO) Program (to S.-H.O.). F.d.L.-P. and L.M.-M. acknowledge financial support from the Spanish Ministry of Economy and Competitivity through projects MAT2017-88358-C3-1-R and MAT2017-88358-C3-2-R and the Aragón Government project Q-MAD. M.P. acknowledges support from the US National Science Foundation (NSF DMR-1905135). M.B.R. acknowledges funding from the US National Science Foundation (NSF CHE-1709822). J.D.C. was supported by the Office of Naval Research Grant N00014-18-12107. S.-H.O. further acknowledges support from the Sanford P. Bordeau Chair in Electrical Engineering at the University of Minnesota.

Author information




D.Y. and S.-H.O. conceived the project and designed experiments. D.Y. performed device design, fabrication and measurements. F.d.L.-P. and L.M.-M. developed theories and performed numerical calculations. D.A.M. and I.-H.L. performed computer simulations. D.Y., F.d.L.-P., M.P., D.A.M., I.-H.L., M.B.R., J.D.C., L.M.-M. and S.-H.O. analysed the results. All authors contributed to interpretation of the results and wrote the paper together.

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Correspondence to Luis Martín-Moreno or Sang-Hyun Oh.

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Supplementary Information

Supplementary Figs. 1–9, Sections 1–11 and Tables 1 and 2.

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Yoo, 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/s41566-020-00731-5

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