Fig. 5: Kerr and Faraday rotation angles in the low-energy tight-binding model of MnBi2Te4.
a Complex Kerr rotation angle \({\phi }_{K}={\tan }^{-1}({r}_{xy}/{r}_{xx})\). b Complex Faraday rotation angle \({\phi }_{F}={\tan }^{-1}({t}_{xy}/{t}_{xx})\). The real and imaginary parts of the complex angles are shown as solid and dashed lines, respectively. We consider the effect of both top and bottom surfaces by using Eqs. (15) and (16) with the refractive indices n1 = 2.2 and n3 = 2.4 for the capsulating media. The complex refractive index of the model itself is obtained from the electric dipole susceptibility through \({n}_{2}(\omega )=\sqrt{1+{\chi }_{xx}(\omega )/{\epsilon }_{0}}\). For LH, we calculate the axion angle from the layer Hall conductivity with periodic boundary conditions and use the thickness of 50 layers for ϕ = n2ωd/c. All optical response functions are calculated with γ = 10 meV to broaden the resonance through ω → ω + iγ.
