Orbital symmetry selective spin characterization of Dirac cone like state on W(110)
The surface of W(110) exhibits a spin orbit induced Dirac cone like surface state, which is of mainly {d}_{{z}{2} orbital character near \overline{\mathrm{\ensuremath{\Gamma} although it is strongly influenced by the twofold \mathrm{C}}_{2v} surface symmetry. Its distinctive k dependent spin polarization along \overline{\mathrm{\ensuremath{\Gamma}\phantom{\rule{0.16em}{0ex}\overline{\mathrm{H} is revealed by spin and angle resolved photoemission excited with $p$ and $s$ polarized light. The spin texture of the surface state is found to change sign upon switching from $p$ to $s$ polarized light. Based on electronic structure calculations, this behavior is explained by the orbital composition of the Dirac cone like state. The dominant part of the state has even mirror symmetry and is excited by $p$ polarized light. A minor part with odd symmetry is excited by $s$ polarized light and exhibits a reversed spin polarization. Our study demonstrates in which way spin orbit interaction combines the spin degree of freedom with the orbital degree of freedom and opens a way to manipulate the spin information gathered from the Dirac cone like surface state by light. Our results prove that `spin control' is not restricted to topological surface states with $p$ type orbital symmetry in topological insulators.