Ferroelectric domain wall phonon polarizer

Modulating the polarization of a beam of quantum particles is a powerful method to tailor the macroscopic properties of the ensuing energy flux as it directly influences the way in which its quantum constituents interact with other particles, waves, or continuum media. To date, practical polarizers, being well developed for electric and electromagnetic energy, have not yet been proposed for heat fluxes carried by phonons. Here, we report on atomistic phonon transport calculations demonstrating that ferroelectric domain walls can operate as phonon polarizers when a heat flux pierces them. Our simulations for the representative ferroelectric perovskite PbTiO3 show that the structural inhomogeneity associated with the domain walls strongly suppresses transverse phonons, while longitudinally polarized modes can travel through multiple walls in series, largely ignoring their presence.