Dirac semimetal-assisted near-field radiative thermal rectifier and thermostat based on phase transition of vanadium dioxide.

Abstract

The near-field thermal radiation has broad application prospects in micro-nano-scale thermal management technology. In this paper, we report the Dirac semimetal-assisted (AlCuFe quasicrystal) near-field radiative thermal rectifier (DSTR) and thermostat (DST), respectively. The DSTR is made of a Dirac semimetal-covered vanadium dioxide (VO2) plate and silicon dioxide (SiO2) plate separated by a vacuum gap. The left and right sides of DST are consisted of the SiO2 covered with Dirac semimetal, and the intermediate plate is the VO2. The strong coupling of the surface electromagnetic modes between the Dirac semimetal, SiO2, and insulating VO2 leads to enhance near-field radiative transfer. In the DSTR, the net radiative heat flux of VO2 in the insulating state is much larger than that in metallic state. When the vacuum gap distance d=100 nm, Fermi level EF=0.20 eV, and film thickness t=12 nm, the global rectification factor of DSTR is 3.5, which is 50% higher than that of structure without Dirac semimetal. In the DST, the equilibrium temperature of the VO2 can be controlled accurately to achieve the switching between the metallic and insulating state of VO2. When the vacuum gap distance d=60 nm, intermediate plate thickness δ=30 nm, and film thickness t=2 nm, with the modulation of Fermi level between 0.05-0.15 eV, the equilibrium temperature of VO2 can be controlled between 325-371 K. In brief, when the crystalline state of VO2 changes between the insulating and metallic state with temperature, the active regulation of near-field thermal radiation can be realized in both two-body and three-body parallel plate structure. This work will pave a way to further improve performance of near-field radiative thermal management and modulation.