Interlayer electron–phonon coupling in WSe2/hBN heterostructures

The emergence of optically silent phonons show that strong interlayer electron–phonon coupling can arise in van der Waals heterostructures, with the vibrational modes in one layer coupling to the electronic states in a neighbouring layer. Engineering layer–layer interactions provides a powerful way to realize novel and designable quantum phenomena in van der Waals heterostructures1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16. Interlayer electron–electron interactions, for example, have enabled fascinating physics that is difficult to achieve in a single material, such as the Hofstadter’s butterfly in graphene/boron nitride (hBN) heterostructures5,6,7,8,9,10. In addition to electron–electron interactions, interlayer electron–phonon interactions allow for further control of the physical properties of van der Waals heterostructures. Here we report an interlayer electron–phonon interaction in WSe2/hBN heterostructures, where optically silent hBN phonons emerge in Raman spectra with strong intensities through resonant coupling to WSe2 electronic transitions. Excitation spectroscopy reveals the double-resonance nature of such enhancement, and identifies the two resonant states to be the A exciton transition of monolayer WSe2 and a new hybrid state present only in WSe2/hBN heterostructures. The observation of an interlayer electron–phonon interaction could open up new ways to engineer electrons and phonons for device applications.