Coherent heat transport in graphene grain boundary superlattices

Abstract Superlattice can effectively regulate the physical properties of nanomaterials due to the periodic arrangement of layered crystalline structure. Especially in the field of heat transport superlattice is widely concerned because of the existence of coherent and incoherent phonon transport. Many theoretical and experimental studies have investigated superlattices formed by alternating of two similar lattices. However, there are few studies on the grain boundary superlattices composed of twin crystals. Here, we focus on phonon heat transport in the graphene grain boundary superlattice using a wide-scale molecular dynamics simulation. We demonstrate that there is a minimum thermal conductivity in the transition from incoherent transport to coherent transport with the decrease of period length of graphene superlattice on grain boundary in the diffusion transport regime. An interesting phenomenon of size effect with like-ballistic-diffusion transport is found under periodic boundary conditions in the superlattice. We also observe a minimum thermal conductivity in the direction along the grain boundary, which provides a new idea for the design of controllable thermal management materials based on graphene superlattices.