Violation of reciprocal radiation by metamaterial of Ge/Si/Weyl semimetal with small incident angle of 5°

Nonreciprocal heat radiation is essential for effective heat management and enhancing heat harvest efficiency. However, developing an efficient nonreciprocal device that supports both polarizations poses a significant challenge, especially under conditions of small-angle incidence. In response to this problem, we propose a high-efficiency nonreciprocal heat radiation device tailored for small-angle incidence. The device comprises an array of germanium-based (Ge) nanocylinders, a silicon (Si) layer, a Weyl semimetal (WSM) layer, and a reflective silver (Ag) layer. Utilizing numerical computations via the rigorous coupled-wave analysis (RCWA) method and validating the findings through the finite element method (FEM), our research demonstrates significant nonreciprocity in both TE and TM polarizations at a wavelength of 15.4915 μm. The underlying physical mechanism is further elucidated through impedance matching theory. Additionally, we investigate how the two polarization channels evolve across a broad range of structural parameters, providing valuable insights for practical implementation. The proposed device showcases strong nonreciprocity for both polarizations under small-angle incidence, offering significant advancements for nonreciprocal heat radiation technologies.