Moiré phonons in twisted MoS₂ bilayer. (a) and (b) Raman spectra of twisted MoS₂ bilayer in the regions of (a) 50–365 cm⁻¹ and (b) 370–425 cm⁻¹. The Raman modes in different phonon branches are represented by different shapes and color symbols. The Raman spectra of monolayer MoS₂ and 3R-bilayer MoS₂ (θ =0°) are plotted for comparison. (c) and (d) The comparison of calculated and experimental frequencies of moiré phonons dependent on θ (c) and | g | (d), | g | is the magnitude of the basic vector of the moiré reciprocal lattices. Reprinted with permission from Ref. [90]. Copyright 2018, American Chemical Society.