Radiative Thermal Diode via Hyperbolic Metamaterials

Hyperbolic metamaterials (HMMs) support propagating waves with arbitrarily large wavevectors over broad spectral ranges, and are uniquely valuable for engineering radiative thermal transport in the near field. Here, by employing a rational-design approach based on electromagnetic local density of states, we demonstrate ability HMMs to substantially rectify heat flow. Our idea is establish forward-biased scenario where two HMM-based terminals diode feature overlapped hyperbolic bands which result current, suppress reverse flow creating spectrally mismatched states as temperature bias flipped. As an example, present few high-performance diodes pairing made polar dielectrics metal-to-insulator transition materials form periodic nanowire arrays, considering three representative kinds substrates. Upon optimization, theoretically achieve rectification ratio 324 at 100-nm gap, remains greater than 148 larger gap sizes up 1 \textmu{}m wide range. The maximum represents almost 1000-fold increase compared bulk using same materials, twice that state-of-the-art designs. work highlights potential rectifying flow, may find applications advanced thermal-management energy-conversion systems.