Impact of moiré superlattice on atomic stress and thermal transport in van der Waals heterostructures

Moiré superlattices and their interlayer interactions in van der Waals heterostructures have received surging attention for manipulating the properties of quantum materials. In this work, based on non-equilibrium molecular dynamics simulations, we find that the in-plane thermal conductivity of graphene/hexagonal boron nitride (h-BN) moiré superlattices decreases monotonically with the increase in the interlayer rotation angle within the small twisting range. The atomic stress amplitude exhibits the periodic distribution corresponding to a structural moiré pattern. Through the in-depth analysis at the atomic level, a competing mechanism between the magnitude and the directional change of the in-plane heat flow has been revealed, and the dominant role of directional change in determining the in-plane thermal conductivity of graphene/h-BN moiré superlattices at small rotation angle has also been confirmed. Finally, the monotonic decreasing trend of in-plane thermal conductivity at a small rotation angle is further explained by the reduced low-frequency phonon transmission and the blue shift of the transmission peak as the interlayer rotation angle increases. Our work provides the physical understanding of the moiré superlattice effect and a new approach for regulating the thermal conductivity of two-dimensional materials.