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

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.