2013年5月8日 13時30分 理学館506

We study the three-dimensional (3D) momentum-resolved electronic structure of bulk Platinum metal, which is known to show the largest ‘spin-Hall conductivity’ of all materials[1]. We measure circular-dichroism in the valence band dispersions and Fermi surfaces using soft x-ray angle resolved photoemission spectroscopy. The experimentally measured band dispersions and Fermi surfaces are consistent with band structure calculations including spin-orbit coupling[2]. However, the hexagonal Fermi surface around L point which shows negligible effects due to spin-orbit coupling, exhibits a large oscillatory circular dichroism with a period of 2π/3 radians. In contrast, the three lobe-shaped Fermi surfaces around L point derived from strong spin-orbit coupled states, show circular dichroism with a periodicity of 2π radians. The observed Fermi surface dependent circular dichroism can be associated with the theoretically known ‘orbital-Hall’ and ‘spin-Hall’ conductivity components[3]. We propose that the momentum dependent circular dichroism on the Fermi surfaces tracks the effective Aharonov-Bohm phase due to ‘orbital’ and ‘pseudo-spin’ texture in bulk Platinum metal, respectively.