Giant tunable nonreciprocity of light in Weyl semimetals

The propagation of light in Weyl semimetal films is analyzed. The magnetic\nfamily of these materials is known by anomalous Hall effect, which, being\nenhanced by the large Berry curvature, allows one to create strong gyrotropic\nand nonreciprocity effects without external magnetic field. The existence of\nnonreciprocal waveguide electromagnetic modes in ferromagnetic Weyl semimetal\nfilms in the Voigt configuration is predicted. Thanks to the strong dielectric\nresponse caused by the gapless Weyl spectrum and the large Berry curvature,\nferromagnetic Weyl semimetals combine the best waveguide properties of magnetic\ndielectrics or semiconductors with strong anomalous Hall effect in\nferromagnets. The magnitude of the nonreciprocity depends both on the internal\nWeyl semimetal properties, the separation of Weyl nodes, and the external\nfactor, the optical contrast between the media surrounding the film. By tuning\nthe Fermi level in Weyl semimetals, one can vary the operation frequencies of\nthe waveguide modes in THz and mid-IR ranges. Our findings pave the way to the\ndesign of compact, tunable, and effective nonreciprocal optical elements.\n