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

Abstract

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 Γ̄ point, and two spin-polarized branches cross at Γ̄. 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 topology. © 2012 American Physical Society.