Tunable Giant Spin Hall Conductivities in a Strong Spin-Orbit Semimetal: Bi1-xSbx

Intrinsic spin Hall conductivities are calculated for strong spin-orbit Bi1-xSbx semimetals, from the Kubo formula and using Berry curvatures evaluated throughout the Brillouin zone from a tight-binding Hamiltonian. Nearly crossing bands with strong spin-orbit interaction generate giant spin Hall conductivities in these materials, ranging from 474 (h/e) (Omega cm)(-1) for bismuth to 96 (h/e) (Omega cm)(-1) for antimony; the value for bismuth is more than twice that of platinum. The large spin Hall conductivities persist for alloy compositions corresponding to a three-dimensional topological insulator state, such as Bi0.83Sb0.17. The spin Hall conductivity could be changed by a factor of 5 for doped Bi, or for Bi0.83Sb0.17, by changing the chemical potential by 0.5 eV, suggesting the potential for doping or voltage tuned spin Hall current.