Radiative Thermal Switch Exploiting Hyperbolic Surface Phonon Polaritons

We study the radiative heat flux between two nanoparticles in close vicinity to the natural hyperbolic material $h$-BN, with its optical axis oriented parallel to the interface. We show that the heat flux between the nanoparticles can be efficiently modulated when rotating the nanoparticles due to the coupling to the highly directional hyperbolic surface modes in $h$-BN. Finally, we discuss the thickness and distance dependence of this effect.