Origin of Interlayer Exciton–Phonon Coupling in 2D Heterostructures

The coupling between excitons and phonons across adjacent layers has been experimentally observed in various heterostructures of layered materials. However, the precise mechanism underlying this phenomenon remains elusive. Using the WSe₂@<i>h</i>BN heterostructure as an example, we study the origin of the interlayer exciton-phonon coupling and its signature in resonant Raman scattering through first-principles calculations. Our study emphasizes the central role of crystal symmetries in the interlayer exciton-phonon scattering processes, which are responsible for the anomalous resonant Raman intensities of the in-plane and the out-of-plane <i>h</i>BN phonon modes. We find that the deformation potential induced by the <i>h</i>BN phonon interacts with the hybridized hole density of WSe₂ excitons near the <i>h</i>BN interface, leading to interlayer exciton-phonon coupling.