Unexpected thermal conductivity enhancement in pillared graphene nanoribbon with isotopic resonance

Wave effects of phonons play an important role in modulating thermal transport in nanostructures. In this paper, we calculated the thermal conductivity of a species of graphene nanoribbon phononic metamaterials (GNPM), pillared graphene nanoribbon, through nonequilibrium molecular dynamics. Interestingly, it is found that the thermal conductivity of GNPM is enhanced by isotopic resonance at pillars, which is in contrast to the reduction by isotopic doping. Furthermore, mode-analysis and atomic Green's function calculations reveal that the mechanism of enhancement originates from the broken hybridization. Additionally, we calculated the effects of the ribbon's width and pillars' height on the thermal conductivity of GNPM. The isotopic resonance provides a mechanism to manipulate phonon transport in nanostructures.