Interlayer\nExciton–Phonon Coupling in MoSe₂/WSe₂ Heterostructures

Abstract

Transition metal dichalcogenide heterostructures have\ngarnered\nstrong interest for their robust excitonic properties, mixed light–matter\nstates such as exciton-polaritons, and tailored properties, vital\nfor advanced device engineering. Two-dimensional heterostructures\ninherit their physics from monolayers with the addition of interlayer\nprocesses that have been particularly emphasized for their electronic\nand optical properties. Here, we demonstrate the interlayer coupling\nof the MoSe₂ phonons to WSe₂ excitons in a WSe₂/MoSe₂ heterostructure using resonant Raman scattering.\nThe WSe₂ monolayer induces an interlayer resonance in the\nRaman cross-section of the MoSe₂ A_1g phonons.\nFrozen-phonon calculations within density functional theory reveal\na strong deformation-potential coupling between the A_1g MoSe₂ phonon and the electronic states of the close-by\nWSe₂ layer approaching 20% of the intralayer coupling to\nthe MoSe₂ electrons. Understanding the vibrational properties\nof van der Waals heterostructures requires going beyond the sum of\ntheir constituents and considering cross-material coupling.