Multi-band nonreciprocal thermal radiation based on Weyl semimetals with epsilon-near-zero multilayers

Although various nonreciprocal thermal emitters have been suggested to break the balance between absorption and emission, few structures can achieve strong nonreciprocity in more than three bands. To break this constraint, we propose a nonreciprocal thermal emitter device based on GaN/AIN/SiC/Weyl semimetal (WSM), which is capable of three discrete pairs of near-perfect absorption and emission, leading to perfect hexa-band strong nonreciprocal radiation. The enhanced nonreciprocal thermal radiation is attributed to the field enhancement of epsilon-near-zero layer and nonreciprocal guided resonances excited in the WSM film. By studying the magnetic field distribution, the physical mechanism of multi-band nonreciprocal thermal radiation is revealed, which can be verified by the impedance matching theory. Furthermore, the dependence of the structure dimensions and the axial vector b of the Weyl semimetal on the performance of the nonreciprocal radiation is investigated in detail. We believe that this work can provide an approach to the development of energy conversion devices and frequency selective detectors.