Omnidirectional and near-unity nonreciprocal thermal radiation with trilayer cavities-enhanced approach.

From the standpoint of thermal radiation, omnidirectional nonreciprocal thermal radiation (NTR) is strongly desired for thermal energy harvesting. Here, we propose theoretically lithographic free thermal emitter made in a dielectric-Weyl semimetal (WSM)-dielectric fashion and terminated by a metallic substrate. By engineering the structural parameters, a surprising result of spectrally selective as well as omnidirectional (along both polar and azimuthal angles) NTR is realized.