Atomistic Green’s Function for Thermal Interface Modeling

Atomistic Green’s function (AGF) is a powerful tool for studying phonon transmission across single and multiple interfaces. In this talk, I will share my journey with AGF. Dr. Mingo was the first one to introduce AGF method and I learned tremendously from his 2003 PRB paper. I first applied the AGF to a single Si/Ge interface with first-principles inputs and observed enhanced phonon transmission by atomic roughness. I then employed AGF to Si/Ge superlattices and studied the effects of aperiodicity and roughness on coherent phonon transport. We later combined AGF with Bayesian optimization to gain insights into thermal interface doping strategies to enhance the conductance. By taking one step further to decompose phonon transmission onto individual phonon modes, we directly observed phonon Anderson localization in Si/Ge aperiodic superlattices. One of the biggest and persistent challenges in traditional AGF is that it was formulated in the harmonic framework and neglected the inelastic scattering. Dr. Mingo developed anharmonic AGF for a molecular junction in 2006. Inspired by his work, we developed a rigorous anharmonic AGF for 3D interfaces with first-principles inputs. We showed that for interfaces between two dissimilar materials, more channels can be opened by inelastic scattering. We later used this framework to demonstrate the nanoscale thermal interface rectification in the quantum regime.

This presentation is in memory of Dr. Natalio Mingo.