Spin-orbit dichroism in SX-ARPES of Pt(111)

We study the bulk electronic structure of Pt(111) using polarization dependent soft x-ray (SX)-ARPES ($h\nu$=450--610 eV). Pt is known to exhibit the largest spin Hall conductivity of all metals, which is derived from its large spin orbit coupling [1,2]. We have measured band dispersions along $\Gamma$-K-X ($h\nu$=466 eV) with clockwise and counterclockwise circularly polarized x-rays and obtained circular dichroism (CD) in the valence band of Pt. A comparison with calculated band dispersions including spin-orbit coupling gives a very good match with the experimental results [3,4], thus establishing the role of spin-orbit coupling in the electronic structure of Pt. Our results also identify (i) a hybridization gap with symmetry switching dichroism and (ii) strong CD of bands at the Fermi level, which provide the carriers responsible for SHE.\\[0pt] [1] T.~Kimura, {\it et al.}, Phys.~Rev.~Lett.~{\bf 98}, 156601 (2007). [2] M.~Morota, {\it et al.}, arXiv:1008.0158v1. [3] G.~Y.~Guo, {\it et al.}, Phys.~Rev.~Lett.~{\bf 100}, 096401 (2008). [4] A.~D.~Corso and A.~M.~Conte, Phys.~Rev.~B {\bf 71}, 115106 (2005).