Metric for quantifying elastic and inelastic thermal transport at interfaces

Understanding interfacial thermal transport across interfaces is crucial for unraveling heat transfer mechanisms in materials and devices. Interestingly, an effective metric to quantify the contributions from elastic and inelastic vibration scatterings at interfaces to interfacial thermal transport is still lacking. In this paper, we demonstrate that the significance of elastic and inelastic vibration scatterings at the interfaces on the interfacial thermal transport is determined by the competition between the similarity of vibrational density of states (VDOS) between two contacted leads and the anharmonicity of the interface. The VDOS similarity between two contacted leads, measured using the Kullback-Leibler (K-L) divergence value, is found to correlate strongly to the signature of elastic thermal transport at interfaces. Our calculations show that elastic vibration scatterings dominate the interfacial thermal transport at interfaces when its K-L divergence value is <0.2. For instance, the elastic vibration scatterings contribute >75% to the interfacial thermal conductance (ITC) of Ar/heavy Ar (h-Ar) interfaces when the K-L divergence value is <0.2. When the K-L divergence value is >0.2, which indicates the VDOS similarity between two contacted leads is significant, we find that both the elastic and inelastic vibration scatterings at interfaces contribute primarily to the interfacial thermal transport. Furthermore, for the interfaces with K-L divergence values >1, the ratio of ITC contributed by inelastic vibration scatterings can be quantitatively characterized by the interfacial anharmonic ratio (IAR), which is a measure of interfacial anharmonicity. Our calculations on Ar/h-Ar, Si/Al, and Si/Ge interfaces at various temperatures with K-L divergence values >1 show that the IAR is generally linear with the inelastic contribution to ITC with an error of 12.5%. Our results here advance the fundamental understanding of interfacial thermal transport resulting from elastic or inelastic vibration scatterings, which may benefit the thermal management design in related applications.