Polarization-Resolved Study of Phonon Scattering from Embedded Nanoparticles

Nanoparticle-in-alloy material systems are promising candidates for high efficiency thermoelectric materials, due to their greatly reduced lattice contribution to thermal conductivity. In this talk, we use a recently developed frequency-domain perfectly matched layer computational technique to calculate the scattering cross sections of embedded nanoparticles across the entire Brillouin zone and for all phonon modes including transverse acoustic phonons and optical phonons for the first time. For acoustic modes, we compare the computational results against previously used results from continuum mechanics and find excellent agreement so long as the Mie regime is accurately represented within the continuum mechanics models. Interestingly, we find that the interaction of optical phonons is remarkably different compared to its acoustic counterparts, with scattering efficiencies of optical phonons in the Raleigh regime observed to be up to 10-fold higher than acoustic phonons. Furthermore, we show that an interdiffused nanoparticle/matrix is more effective at scattering phonons compared to solids nanoparticle with the same net impurity concentration, with scattering efficiencies 2-fold higher in the dominant heat carrying regions.