Large non-reciprocal absorption and emission of radiation in type-I ferromagnetic Weyl semimetals

The equality between the spectral, directional emittance and absorptance of an object under local thermal equilibrium is known as Kirchhoff's law of radiation. The breakdown of Kirchhoff's law of radiation is physically allowed by breaking time-reversal symmetry and can open new opportunities for novel non-reciprocal light emitters and absorbers. In this work, we show via simulation that ferromagnetic type-I Weyl semimetals, due to their large anomalous Hall effect, can exhibit large non-reciprocal emittance and absorptance without an external magnetic field by coupling light into non-reciprocal surface plasmons modes. This work points to the applicability of type-I ferromagnetic Weyl semimetals for magneto-optical and energy applications.