Prior theoretical studies found a large temperature window around 100 K for hydrodynamic phonon transport to occur in monolayer graphene and other layered materials due to dominant momentum-conserving normal scattering processes. However, these studies have yet to account for high-order phonon scattering processes, especially four-phonon scattering that may play an important role and limit the thermal conductivity of graphene at temperatures above 300 K based on some recent predictions. Here, the predicted four-phonon scattering rates are incorporated into a deviational Monte Carlo solution of the Peierls-Boltzmann equation of phonons in monolayer graphene. The results reveal the apparent weakening of hydrodynamic features, including phonon Poiseuille flow and second sound behaviors, even at 100 K temperature. This effect is connected to the predicted increase of momentum-destroying Umklapp scattering in the calculated four-phonon processes. These findings point to the need for further studies of the effects of high-order phonon scattering, including second-order perturbation theory of three-phonon processes, of various materials in non-Fourier lattice thermal transport phenomena.

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• Lattice thermal conductivity
• Second sound
• Graphene
• Boltzmann theory
• Density functional calculations
• Monte Carlo methods