Extremely Confined Acoustic Phonon Polaritons in Monolayer-hBN/Metal Heterostructures for Strong Light–Matter Interactions
Zhu Yuan, Runkun Chen, Peining Li, Alexey Y. Nikitin, Rainer Hillenbrand, Xinliang Zhang
Abstract
Phonon polaritons in polar van der Waals materials enable strong electromagnetic-field confinement and enhancement for deeply subwavelength scale light-matter interactions. Here we propose and theoretically study acoustic phonon polaritons (APhPs) supported by a monolayer of hexagonal boron nitride (hBN) located at a few nanometers distance above a metal substrate. Compared to conventional hBN phonon polaritons, APhPs exhibit much larger polariton confinement, stronger near-field enhancement, and slower group velocity, altogether with nearly identical polariton lifetimes. These remarkable properties allow APhP-based nanoresonators to significantly enhance vibrational fingerprints of subnanometer-thick molecule layers, achieving strong coupling between molecular vibrations and APhP modes. Our work demonstrates the great potential of APhPs for exploring strong light–matter interactions at an extremely deep subwavelength-scale.