Experimental Observation of Nonreciprocal Reflection in a Magnetic Weyl Semimetal at Zero Applied Field

The discovery of magnetic Weyl semimetals has inspired a flurry of investigation into the magneto-optical responses of such topological semimetals. In this work, we demonstrate modulation of the non-reciprocal p-polarized reflection coefficient by reversing the orientation remanent magnetization in a magnetic Weyl semimetal. Previously, measurements of nonreciprocity via the transverse magneto-optic Kerr effect, where the amplitude of the p-polarized reflection is modulated with respect to the polarity of a magnetization vector that is transverse to the optical plane, had remained elusive. We observe a net reflectance modulation of nearly 8% in the half-Heusler Co₃Sn₂S₂ at 80K without the concurrence of an external applied magnetic field, nearly an order of magnitude higher than previous measurements of the transverse magneto-optical Kerr effect in ferromagnets. Our results demonstrate the utility of magnetic Weyl semimetals for magneto-optical metasurfaces, applications in magnetic memory, and energy harvesting. Unlike traditional ferromagnets or magnetic semiconductors where the off-diagonal permittivity is a function of the cyclotronic resonance frequency, the nonreciprocal response of magnetic Weyl semimetals is believed to be governed by the nontrivial Berry curvature that exists between recombinant Weyl nodes. This unique topological effect paves the way for the realization of practical Berrytronic devices.