Nanophononic metamaterials induced proximity effect in heat flux regulation

Abstract

Recent studies have shown that the construction of nanophononic metamaterials can reduce thermal conductivity without affecting electrical properties, making them promising in many fields of application, such as energy conversion and thermal management. However, although extensive studies have been carried out on thermal conductivity reduction in nanophononic metamaterials, the local heat flux characteristic is still unclear. In this work, we construct a heat flux regulator which includes a silicon nanofilm with silicon pillars. The regulator has remarkable heat flux regulation ability, and various impacts on the regulation ability are explored. Surprisingly, even in the region without nanopillars, the local heat current is still lower than that in pristine silicon nanofilms, reduced by the neighboring nanopillars through the thermal proximity effect. We combine the analysis of the phonon participation ratio with the intensity of localized phonon modes to provide a clear explanation. Our findings not only provide insights into the mechanisms of heat flux regulation by nanophononic metamaterials, but also will open up new research directions to control local heat flux for a broad range of applications, including heat management, thermoelectric energy conversion, thermal cloak, and thermal concentrator.