The $C_{2v}$ symmetry of the W(110) surface influences strongly the spin-polarized Dirac-cone-like surface state within a spin-orbit-induced symmetry gap. We present a detailed angle-resolved photoemission study with $s$- and $p$-polarized light alon
g three different symmetry lines. The Dirac-cone-like feature appears along $bar{Gamma}bar{H}$ and $bar{Gamma}bar{S}$, while it is strongly deformed along $bar{Gamma}bar{N}$. A two-fold $Sigma_{3}$ symmetry of the $d$-type surface state is identified from photoemission experiments using linear polarized light. Our results are well described by model calculations based on an effective Hamiltonian with $C_{2v}$ symmetry including Rashba parameters up to third order. The flattened Dirac cone of the surface state is caused by hybridization with bulk continuum states of $Sigma_{1}$ and $Sigma_{2}$ symmetry. The spin texture of this state obtained from the model calculations shows a quasi-one dimensional behavior. This finding opens a new avenue in the study of $d$-electron-based persistent spin helix systems and/or weak topological insulators.
Helical spin textures with the marked spin polarizations of topological surface states have been firstly unveiled by the state-of-the-art spin- and angle-resolved photoemission spectroscopy for two promising topological insulators Bi$_2$Te$_2$Se and
Bi$_2$Se$_2$Te. The highly spin-polarized natures are found to be persistent across the Dirac point in both compounds. This novel finding paves a pathway to extending their utilization of topological surface state for future spintronic applications.
The surface of W(110) exhibits a Dirac-cone-like surface state with $d$ character within a spin-orbit-induced symmetry gap. As a function of wave vector parallel to the surface, it shows nearly massless energy dispersion and a pronounced spin polariz
ation, which is antisymmetric with respect to the Brillouin zone center. In addition, the observed constant energy contours are strongly anisotropic for all energies. This discovery opens new pathways to the study of surface spin-density waves arising from a strong Fermi surface nesting as well as $d$-electron-based topological properties.
The electronic structures of the Heusler type compounds Fe$_{3-x}V$_x$Si in the concentration range between x = 0 and x = 1 have been probed by photoemission spectroscopy (PES). The observed shift of Si 2p core- level and the main valence band struct
res indicate a chemical potential shift to higher energy with increasing x. It is also clarified that the density of state at Fermi edge is owing to the collaboration of V 3d and Fe 3d derived states. Besides the decrease of the spectral intensity near Fermi edge with increasing x suggests the formation of pseudo gap at large x.
