Tunable Giant Spin Hall Conductivities in a Strong Spin-Orbit Semimetal: Bi$_{1-x}$Sb$_x$

TL;DR

This study calculates intrinsic spin Hall conductivities in Bi$_{1-x}$Sb$_x$ semimetals, revealing giant, tunable values driven by strong spin-orbit interactions, with potential for doping or voltage control in spintronic applications.

Contribution

The paper provides the first detailed calculation of spin Hall conductivities in Bi$_{1-x}$Sb$_x$ semimetals, demonstrating their large magnitude and tunability via chemical potential adjustments.

Findings

Giant spin Hall conductivities ranging from 96 to 474 ($ abla$/e)(Ωcm)$^{-1}$.

Conductivities remain large in topological insulator phases.

Tuning chemical potential by 0.5 eV can change conductivity by a factor of five.

Abstract

Intrinsic spin Hall conductivities are calculated for strong spin-orbit Bi$_{1-x}$Sb$_x$ 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 ($\hbar$/e)($\Omega$cm)$^{-1}$ for bismuth to 96 ($\hbar$/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 Bi$_{0.83}$Sb$_{0.17}$. The spin Hall conductivity could be changed by a factor of five for doped Bi, or for Bi$_{0.83}$Sb$_{0.17}$, by changing the chemical potential by 0.5 eV, suggesting the potential for doping or voltage tuned spin Hall current.