Thermal Transport in Graphene Nanomesh: Unraveling the Role of Brillouin Zone Folding, Phonon Localization and Phonon Confinement

Coherent thermal transport has recently become a subject of considerable interest, but whether some intriguing phenomena of phonon coherence (including Brillouin zone folding, phonon localization, and phonon confinement) occur in certain nanostructures remains unclear. We have investigated the thermal transport in graphene nanomesh using molecular dynamics simulations together with first-principles calculations. It is found that the thermal conductivity of nanomesh is significantly reduced compared with graphene, mainly due to the bandgaps, flattened phonon dispersions and reduced phonon group velocities induced by Brillouin zone folding. Meanwhile, the significant decrease in thermal conductivity is induced by phonon localization. Phonon confinement caused by reflecting the optical phonon modes back into the C-H part further leads to the reduction of thermal conductivity. We highlight the coherent mechanism for lowering thermal conductivity, which is useful for manipulating heat conduction for thermoelectrics and thermal insulation applications.