LAUSR

Graphene/hexagonal boron nitride (h-BN) heterostructures assembled by van der Waals (vdW) interactions shows numerous unique physical properties such as the quantum Hall effects, exotic correlated states, which have promising potential applications in the design of novel electronic devices. Understanding thermal transport in such junctions is critical to control the performance and stability of prospective nanodevices. In this work, using non-equilibrium molecular dynamics (NEMD) simulations, we systematically investigate the thermal transport in asymmetric grahene/h-BN vdW heterostructures. It is found that the heat prefers to flow from the monolayer to the multilayer regions, resulting in significant thermal rectification (TR) effect. To determine the optimum conditions for TR, the influences of sample length, defect density, asymmetric degree, ambient temperature and vdW interaction strength are studied. Particularly, we found the TR ratio could be improved by about one order of magnitude via increasing the coupling strength from 1 to 10, which clearly distinguishes from the commonly held notion that the TR ratio is practically insensitive or even decreasing with the interaction strength. Detailed spectral analysis reveals that this unexpected increase of TR ratio can be attributed to heavily modified phonon properties of encased graphene due to enhanced interlayer coupling. Our results elucidate the importance of vdW interactions to heat conduction in nanostructures.