Monitoring anharmonic phonon transport across interfaces in one-dimensional lattice chains.

Abstract

Modeling thermal transport through interfaces has been one of the most challenging problems in nanoscale heat transfer. Although continuous theoretical efforts have been made, there has been no consensus on how to rigorously incorporate temperature effect and anharmonicity. In this paper, we adopt the self-consistent anharmonic phonon concept for nonlinear lattices to investigate phonon propagation within the materials as well as across interfaces based on equilibrium molecular dynamics simulations. Based on linear response theory, we propose an efficient method to calculate the frequency-dependent transmission coefficient in a nonlinear lattice. The transmission spectrum is extracted directly from velocity correlations, which naturally includes anharmonic effects. Phonon renormalization at finite temperature can also be easily handled using the proposed method. Our results are consistent with the atomistic Green's function method at the limit of weak anharmonicity. For nonlinear lattices under high temperatures, the anharmonicity is found to increase the cutoff frequency of the transmission coefficient due to phonon renormalization. Further analysis shows that the anharmonicity also promotes interfacial thermal conductance by causing the redistribution of the spectral flux of the excited vibrational waves during their propogation.