(color online) Snapshots of a phonon wave packet travelling across the MoS₂/graphene interface. The travelling direction is indicated by blue arrows, and brown dashed lines denote the interface. (a) LA, k 0 = 0.02 × 2 π / a , f = 1.90 THz. (b) LA, k 0 = 0.075 × 2 π / a , f = 7.10 THz. (c) TA, k 0 = 0.02 × 2 π / a , f = 1.18 THz. (d) LA, k 0 = 0.075 × 2 π / a , f = 4.41 THz. Reprinted with permission from Ref. [63], copyright (2017) by the Springer.