Ray phononics: thermal guides, emitters, filters, and shields powered by ballistic phonon transport


Manipulation of thermal fluxes is essential in today’s science and technology. However, modern thermal phononics relies on the wave interference of phonons and thus is truly efficient either at sub-kelvin temperatures or atomic scales. We propose an alternative concept of heat manipulation based on the particle picture of phonons and their ballistic transport. We call this concept ray phononics as a thermal analogy of ray optics. Ray phononics is free from limitations of the traditional phononics and enables creating and guiding thermal fluxes in realistic nanostructures regardless of their surface roughness. Our simulations illustrate possible applications of ray phononics for emitting directional heat rays, filtering the phonon spectrum, and even protecting a specific region from a thermal gradient. Finally, we show that the proposed concept is not bound to only low temperatures, and ray-phononic nanostructures can control heat fluxes even at room temperature using modern materials like boron arsenide.

Materials Today Physics 15, 100272 (2020)