Nonreciprocal Photonics Using Surface Waves in the Magnetic Weyl Semimetal Co₃Sn₂S₂

The demonstrations of a large intrinsic anomalous Hall effect and large nonlinear optical response in Weyl semimetals is attributable to the presence of nontrivial Berry curvature in regions of reciprocal space between recombinant Weyl points. We explore the properties of single crystals of the magnetic Weyl semimetal Co₃Sn₂S₂ for non-reciprocal photonics and polaritonic devices. Using Fourier transform infrared spectroscopy and ellipsometry, we characterize the material Mueller matrix at 80K in the MIR range we extract a Kramers Kronig consistent permittivity tensor. With [110]-oriented single crystals, we demonstrate the manifestation of non-equivalent reflection coefficients at +/- 70°, induced through the generation of plasmons with a non-reciprocal dispersion. We find for our sample, the non-reciprocity is maximized at 0.17 eV, where the ratio of diagonal and off-diagonal components of the permittivity diverge. We discuss device designs that exploit these relations for use in magnet-less magneto-optical systems.