Fig. 3: Magneto-optical effects in a monolayer WS₂ on TIG.

a The time-reversal symmetry breaking with an out-of-plane exchange magnetic field provided by TIG induces a spectral splitting and an intensity difference between σ⁻ (blue) and σ⁺ (red) in the ML-WS₂ under the pumping of E_ph. b The observed splitting of ~0.5 nm (~1.7 meV) corresponds to an exchange magnetic field of ~7 T at the temperature of 78 K from the TIG. The splitting is estimated to be ~0.2 nm that is hardly measurable in spectra with the reduced exchange magnetic field of ~2.7 T at 298 K. c An alternative method to characterize the magneto-optical effect (Fig. 1C) is using the rotation of linear polarization (blue arrows) of light upon reflection. d A differential reflection spectrum, defined as the difference in reflectance of the sample (WS₂) and substrate (TIG) normalized to that of a reference (silver mirror), consists of a peak of light-matter interaction at the wavelength of ~617 nm. e Analysis of the polarization of reflected light from WS₂ at 617 nm with up (purple) and down (yellow) magnetic moments. The 0° represents that the polarization of the output and input light is the same. The minima of curves designate the polarization of the outgoing light showing a rotation angle of ~2° compared to that of the input light. By flipping the exchange magnetic field (B ↑ and B ↓), the rotation angle changes the sign indicating that the rotation is due to the magneto-optical effect. In the absence of the exchange magnetic field, the polarization of the light reflected from a reference silver mirror (inset) is the same as that of the input light, which manifests as the minimum at 0°, further confirming the magneto effect being the origin of the rotation. The error bar of ±0.5° is system uncertainty.