Characteristics of distinct thermal transport behaviors in single-layer and multilayer graphene

As a crucial signature of hydrodynamic phonon transport, second sound is currently raising research attention in the field of non-Fourier heat conduction. In this work, through molecular dynamics simulations, the fundamental characteristics of second sound are explored from a transient heat conduction modeling in the single-layer and multilayer graphene and graphite. Our simulation results demonstrate that second sound can carry more heat energy and maintain for a longer lifetime than that of the ballistic pulse. The underlying mechanisms are carefully discussed from the modal energy analysis. In addition, we also unveil that the thickness in multilayer graphene and graphite significantly suppresses the propagation of second sound due to the enhanced weight of umklapp scattering. The effects of excitation temperature and ambient temperature on the second sound are also studied. Our simulation results reveal that the second sound in single-layer graphene can persist up to 110 K. This work provides valuable insight into the basic characteristics of second sound, which should be critical in the understanding of hydrodynamic phonon transport and thermal physics in graphene and its derivatives.