Emergent trion-phonon coupling in atomically reconstructed MoSe2−WSe2 heterobilayers

In MoSe${}_{2}$-WSe${}_{2}$ heterobilayers, a coupling of negatively charged excitons to the interlayer shearing motion of the two atomically thin layers is observed in low-frequency resonant Raman experiments. The resonant coupling of the interlayer shear mode and the charged exciton is enabled by the strong hybridization of $Q$-valley states of the heterobilayer, as confirmed by first-principles calculations.