Graphene-assisted near-field radiative thermal rectifier based on phase transition of vanadium dioxide (VO₂)

We report a graphene-assisted near-field radiative thermal rectifier (GTR) made of a graphene-covered VO₂plate and a silicon dioxide (SiO₂) plate separated by a vacuum gap. In framework of fluctuating electrodynamics and fluctuation-dissipation theorem, a comprehensive calculation is performed on near-field radiative heat flux at different chemical potential values and different vacuum gaps. The near-field radiative thermal rectifier (TR) made of a VO₂plate and a SiO₂plate separated by a vacuum gap is also included for comparison purpose. Being compared with TR, GTR with 0.3 eV chemical potential has a great advantage in total rectification factor φ under 200 nm vacuum gap when hot and cold temperatures of the rectifier are kept at 353 K and 300 K, respectively. Total rectification factor φ as high as 3.8 for GTR can be reached at 10 nm vacuum gap and 0.3 eV chemical potential due to strong interplay between p-polarized surface plasmon polaritons (SPPs) of graphene and p-polarized surface phonon polaritons (SPhPs) of SiO₂when hot and cold temperatures of the recitfier are kept at 353 K and 300 K, respectively. This value amounts to almost 1.69 times that for TR at same conditions. This work will pave a way to further improve performance of near-field radiative thermal rectifier and be valuable to research in near-field radiative thermal management and modulation.