Fig. 1: Fermi arcs in a 2D topological ferromagnet.
a Experimental geometry for the spin-, orbital-, and momentum-resolved photoelectron study of the Fermi surface. The magnetization M and the spin polarization Py are oriented in-plane along the y axis, i.e., the crystallographic \([1\bar{1}0]\) direction. b, c Spin-resolved photoemission momentum maps at the Fermi energy EF for b 12 MLs and c 2 MLs Fe films grown on W(110), measured with a photon energy of hν = 50 eV for a sample magnetization pointing into −y direction. The spin polarization Py is indicated by red and blue colours, and the colour strength encodes the intensity. d Schematic evolution of the Fermi-surface topology for the appearance of surface arcs upon breaking TR symmetry. Red (blue) colour denotes spin-up (spin down) electron states, the green circle denotes the spin-orbit mediated hybridization, and black lines indicate the emergent surface Fermi arcs.
