Tunable phononic thermal transport in two-dimensional C6CaC6 via guest atom intercalation

The graphite intercalation compounds have attracted wide interest due to the superconductivity. In this work, the thermal transport in bilayer graphene intercalated with Ca atoms (C6CaC6) at room temperature is studied by using non-equilibrium molecular dynamics simulations. Our simulation results show that the in-plane lattice thermal conductivity (κL) of C6CaC6 is significantly lower than that of the bilayer graphene. The detailed phonon mode analysis reveals that the reduction of κL is because of the mode hybridization and flatbands induced by the intercalated Ca atoms, leading to the decrease in phonon group velocity and the enhancement of phonon scattering. Unlike the role of van der Waals interactions in multilayer graphene and supported graphene, increasing coupling strength between intercalated Ca atoms and graphene brings an enhanced κL in C6CaC6. The spectral phonon analysis uncovers that such anomalous phenomenon is caused by the redistribution of phonon scattering phase space originated from the shift of the flatbands. This study indicates that atom intercalation is an effective way to regulate the heat transport in two-dimensional materials.