Three-dimensional bulk band dispersion in polar BiTeI with giant   Rashba-type spin splitting
  In layered polar semiconductor BiTeI, giant Rashba-type spin-split band dispersions show up due to the crystal structure asymmetry and the strong spin-orbit interaction. Here we investigate the 3-dimensional (3D) bulk band structures of BiTeI using the bulk-sensitive $h\nu$-dependent soft x-ray angle resolved photoemission spectroscopy (SX-ARPES). The obtained band structure is shown to be well reproducible by the first-principles calculations, with huge spin splittings of ${\sim}300$ meV at the conduction-band-minimum and valence-band-maximum located in the $k_z=\pi/c$ plane. It provides the first direct experimental evidence of the 3D Rashba-type spin splitting in a bulk compound. 
M. Sakano, J. Miyawaki, A. Chainani, Y. Takata, T. Sonobe, T.   Shimojima, M. Oura, S. Shin, M. S. Bahramy, R. Arita, N. Nag...
cond-mat.mtrl-sci