Spin Hall effect in iron-based superconductors: A Dirac-point effect
  We have theoretically explored the intrinsic spin Hall effect (SHE) in the iron-based superconductor family with a variety of materials. The study is motivated by an observation that, in addition to an appreciable spin-orbit coupling in the Fe 3d states, a character of the band structure in which Dirac cones appear below the Fermi energy may play a crucial role in producing a large SHE. Our investigation does indeed predict a substantially large spin Hall conductivity in the heavily hole-doped regime such as KFe$_2$As$_2$. The magnitude of the SHE has turned out to be comparable with that for Pt despite a relatively small spin-orbit coupling, which we identify to come from a huge contribution from the gap opening induced by the spin-orbit coupling at the Dirac point, which can become close to the Fermi energy for the heavy hole doping. 
Sudhakar Pandey, Hiroshi Kontani, Dai S. Hirashima, Ryotaro Arita, and   Hideo Aoki
cond-mat.str-el cond-mat.mes-hall cond-mat.mtrl-sci cond-mat.supr-con