Metamaterials for Manipulating Thermal Radiation: Transparency, Cloak, and Expander

Thermal metamaterials are typically designed to work at room temperature, where thermal conduction (mediated by phonons) is the dominant mode of heat transfer. Unfortunately, at higher temperatures thermal radiation (mediated by photons) dominates, and those metamaterials no longer work. Thus the authors propose an effective-medium theory for manipulating thermal radiation described by the Rosseland diffusion approximation. They proceed to design radiative metamaterials that are well-behaved in both steady and transient states, for three different functions. These results may inspire innovations in heat management, including radiative camouflage and thermal diodes.