Coupled electron-phonon thermal transport across metal-nonmetal interfaces and superlattices

Understanding the thermal transport across metal/nonmetal interface is of great importance for applications like electronic and thermoelectric devices. In nonmetal phonons are the dominant heat carriers; while in metal both electrons and phonons conduct heat. The nonequilibrium carrier populations and the complicated coupling channels at the interfaces make our current understanding yet to be completed. In this work, we utilize the fully coupled Monte Carlo simulations to study thermal transport across the metal-nonmetal interfaces and superlattice. The mode-wise electron and phonon relaxation times and their coupling strengths are obtained from first-principles calculations, while the phonon transmissions at interfaces are obtained from the Green’s function methods. The simulation results show that the thermal transport at metal/nonmetal interface can be enhanced by inserting an intermediate metal layer with high electron-phonon coupling strength. For metal-nonmetal superlattice structure, thin metal layers with weak electron-phonon coupling can largely impede the thermal transport. The simulation results reveal the importance of mode-wise scattering channel and the nonequilibrium between electron, acoustic phonon, and optical phonon at the interface to thermal transport.