Fig. 4: Spin texture and Berry curvature of the Fermi arcs in the 2D topological ferromagnet.

a Measured spin-resolved Fermi arcs in 2 MLs Fe/W(110) on the left and on the right side of the momentum map. Colours indicate the in-plane spin component along the x direction, which is orthogonal to the sample magnetization M_−y. The spin polarization P_x is indicated by red and blue colours, and the colour strength encodes the intensity. b Arrows denote the complete theoretical spin texture in momentum space, revealing a prominent non-collinearity for the Fermi arcs (red) as compared to the interior states (grey). c Distribution of the theoretical momentum-space Berry curvature \({{{\Omega }}}_{xy}^{{{{{{{{{{\bf{kk}}}}}}}}}}}\) of all occupied bands in 2 MLs Fe/W(110), around one of the pairs of Fermi arcs. A pseudo-logarithmic colour scale and a linear height field are used to represent the local geometrical curvature, and the Fermi surface is indicated by grey lines.