Phonon-Polariton-Mediated\nConfigurable Radiative Thermal\nRouter

Photon-based radiative thermal router, controlling the\nnanoscale\nflow of heat, exhibits exciting potential in energy harvesting and\nthermal management. However, existing studies show that the terminals\nof thermal routers strongly depend on external field manipulations\nor anisotropic materials. To overcome these limitations, we propose\na thermal router consisting of three isotropic particles which are\nplaced in the proximity of a twisted bilayer made of in-plane hyperbolic\nmaterials. By twisting the bilayer to a critical status where a topological\ntransition occurs, the heat flow can be precisely directed from the\nsource to the drain of choice. At the photonic magic twist angle,\nthe dispersion contours become fat; hence, the collimated group velocity\nand the canalization effect allow the directional propagation of energy.\nFurthermore, we demonstrate that the thermal router has good robustness\nagainst the variation in distance between the source and the drain\nparticles and is sensitive to the vertex angle of the isosceles triangle.\nThe thermal router mediated by the twisted bilayer structures can\nbe expanded to many-particle systems due to unidirectional energy\ntransmission. Our findings enrich the controllability of noncontact\nheat exchange at the nanoscale, providing an alternative way for realizing\ndirectional heat flow in nanoscale thermal routers and other related\nheat transfer devices.