| Summary: | Recent studies have suggested that Weyl semimetals were the promising materials to verify Kirchhoff’s law for nonreciprocal materials in experiment. Nevertheless, existing designs based on Weyl semimetals could not achieve perfect nonreciprocal radiation around a wavelength of 10 µm at small angles. Therefore, it is of significant importance to design structures that can realize perfect nonreciprocal radiation at a shorter wavelength and smaller angle. Here, by using attenuated total reflection, we demonstrate that perfect nonreciprocal radiation can be realized at a wavelength of 10 µm at an angle of 30°. The difference between directional emissivity and absorptivity is as large as 0.99, which is the best result until now, as far as we know. The perfect nonreciprocal radiation is attributed to the nonreciprocal guided resonances in the Weyl semimetal film, which is confirmed by the distribution of magnetic field and dispersion relation. Such a design is promising in verifying Kirchhoff’s law for nonreciprocal materials in experiment.
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