Resonant Raman Scattering of Surface Phonon Polaritons Mediated by Excitons in WSe2 Films

Surface phonon polaritons propagating along interfaces of polar dielectrics coexist with excitons in many van der Waals heterostructures, so understanding their mutual interactions is of great interest. Here, we investigate the contribution of type I surface phonon polariton (SPhP) of hBN to the low-temperature resonant-Raman spectra of hBN/WSe2 heterostructures. When the laser energy is such that the scattered photons have energy close to that of the WSe2 excitons, the resonantly enhanced Raman signal enables the characterization of even one monolayer-thick hBN. We are able to explain the signal using transfer matrix method simulations of SPhP dispersions, provided that we assume the Raman scattering to be momentum nonconserving, as could be the case if localized WSe2 exciton states participated in the process. However, we cannot exclude the contribution of the TO and ZO phonons to the measured signal. We further show that resonant Raman scattering from SiO2 SPhP can also be mediated by WSe2.