Spatially-Resolved Non-Equilibrium Phonon Transport Across Nanoscale Interfaces*

Understanding phonon-mediated heat transfer at the nanoscale, to explain heat-dissipation in nanoelectronics, local temperature effects, and new phenomena probed my ultrafast coherent dynamics, presents a theoretical challenge. Further, nanoscale interfaces pose an exciting experimental frontier, with diverse applications from interface-engineering for thermoelectrics to catalytic interfaces and nanotheranostic agents. Despite the ubiquity of these applications, an accurate microscopic description of thermal interface resistance (TIR) remains elusive. To address this, we introduce a new theoretical and computational framework for semi-classical transport with position-, momentum-space, and scattering event resolution. We demonstrate the recursive formalism for phonon transport in a spherical nanoparticle, and highlight new insights made possible using this multi-dimensional resolution. We extend the formalism to handle interfaces explicitly to quantitatively capture TIR for the technologically relevant Si-Ge heterostructure. Finally, we will present preliminary results in coherent and driven phonon effects, now accesible via ultrafast spectroscopies.