Fig. 2: Moiré-tunable interlayer vibrations in the vdW heterostructure.

a Low-frequency chiral Raman spectra of WSe₂/WS₂ moiré superlattice as a function of twist angle. The frequency of interlayer LB and S modes with nearly 0° twist angle is indicated by the blue and gray dashed lines, respectively. The spectra of helicity-changed (σ + σ-) configurations are scaled for clarity by a scale factor of 2. b Schematic of the interlayer LB phonon which couples strongly with IXs because the vibrational mode is directly modulated by the vertical Coulomb-bound electron-hole pair of exciton (left). Moiré-trapped excitons are localized and controlled by the potential wells (right). c Illustration of WSe₂/WS₂ moiré superlattice in real space (top panel) and mini-Brillouin zone generated from the difference between two wavevectors in reciprocal space (bottom panel). The WSe₂/WS₂ moiré superlattice has a larger moiré period with twist angles close to 0° or 60° (left column) than that with twist angles close to 30° (right column). d The twist angle dependence of the LB mode frequency (blue circles). Errors from peak fitting are smaller than the diameter of the circles. The dashed curve shows the twist-angle dependence of the moiré period for reference.