Thermal convection-diffusion crystal for prohibition and modulation of wave-like temperature profiles

Periodic structures have various applications in wave systems, such as atomic crystals, photonic crystals, and phononic crystals. Here, we extend the related physics from wave systems to convection-diffusion systems and propose the concept of thermal convection-diffusion crystals, referring to a periodic porous medium with moving fluid. Phenomenally speaking, only the temperature profiles with allowed frequencies can propagate stably in a thermal convection-diffusion crystal, and those with forbidden frequencies try to change their frequencies for stable propagation. As an application of thermal convection-diffusion crystals, we further design a thermal frequency modulator to manipulate wave-like temperature profiles. These results broaden the application scope of periodic structures in convection-diffusion systems and enlighten further development of thermal management and thermal metamaterials with thermal convection-diffusion crystals.