Large intrinsic spin Hall conductivity and anomalous Hall conductivity in monolayer MnBi2Te4

Recently, the magnetic topological insulator ${\mathrm{MnBi}}_{2}{\mathrm{Te}}_{4}$ was discovered as a great platform to investigate the interplay between magnetism and topology, such as the anomalous Hall effect and the topological magnetoelectric effect. Here, we employ a first-principles approach to investigate the electronic structure of monolayer ${\mathrm{MnBi}}_{2}{\mathrm{Te}}_{4}$. Our calculations reveal a large spin Hall conductivity $[\ensuremath{\sim}844.8 (\ensuremath{\hbar}/\mathrm{e})\mathrm{S}/\mathrm{cm}]$ accompanying the anomalous Hall effect due to the anticrossing bands near the Fermi level. We also surprisingly find an emergent sixfold rotational symmetry for the spin Berry curvature in the large $\mathbit{k}$ region of the Brillouin zone. Based on the symmetry analysis, we conclude that the spin polarization in the band structure is crucial to the emergent symmetry. Our results may provide valuable insights into understanding the large spin Hall conductivity in magnetic topological insulators.