This paper reports the discovery of a gigantic magneto-optical (MO) response in the magnetic Weyl semimetal Co3Sn2S2, stemming from its topological electronic structure and intense Berry curvature. Low-energy MO spectroscopy and first-principles calculations reveal that interband transitions on nodal rings connected to Weyl points cause resonance in optical Hall conductivity, leading to a giant intrinsic anomalous Hall effect (AHE). Terahertz Faraday and infrared Kerr rotations are significantly enhanced by these resonances, showcasing a novel low-energy optical response characteristic of magnetic Weyl semimetals.

Y. Okamura, S. Minami, Y. Kato, Y. Fujishiro, Y. Kaneko, J. Ikeda, J. Muramoto, R. Kaneko, K. Ueda, V. Kocsis, N. Kanazawa, Y. Taguchi, T. Koretsune, K. Fujiwara, A. Tsukazaki, R. Arita, Y. Tokura, Y. Takahashi