Topology of spin polarization of the 5d states on W 110 and Al W 110 surfaces

The spin polarization of W 110 and Al W 110 surfaces is studied by spin and angle resolved photoemission. On both surfaces distinct E k dispersions are identified with an unusual topology A single spectral branch is spin polarized antisymmetrically relative to the Gammabar point, and two spin polarized branches cross at Gammabar . The crossing branches disperse linearly but this similarity to a Dirac cone is lost after deposition of the Al, where they acquire a parabolic dispersion. Based on ab initio one step photoemission theory, we show that the measured spin polarization is a property of the ground state and identify the effect as the counterpart of the recently discovered Rashba polarization of bulk states at the surface, but with a distinct non Rashba topolog