Effectively infinite thermal conductivity and zero-index thermal cloak

Abstract

Thermal conductivities are the key to heat transfer, and high thermal conductivities are generally beneficial and sometimes indispensable to design thermal metadevices. Therefore, the exploration of high thermal conductivities never stops. However, infinite thermal conductivities have not yet been discovered. To solve the problem, we propose an exact approach to effectively infinite thermal conductivities with a constant-temperature boundary condition, which can be easily realized by an external thermostatic sink. Since (effectively) infinite thermal conductivities just correspond to zero refractive indexes in photonics, they have direct applications in designing zero-index thermal metadevices. For example, we experimentally demonstrate zero-index thermal cloaks which can work in highly conductive backgrounds with simple structures. These results provide insights into thermal metadevices and thermal management with effectively infinite thermal conductivities.