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 along 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.
Categories: cond-mat.mes-hall