Spin-orbit torque in two dimensional antiferromagnetic topological insulators

Topological insulators (TI) have been found to be a source of huge spin-orbit torque (SOT) \footnote{Y. Fan et. al., Nat. Nanotechnol. 11, 352 (2016).} that originates from their surface states. However, the proximity of a ferromagnetic layer can destroy the surface states which makes the exact nature of the SOT quite argumentative. Recently it has been found that in presence of an antiferromagnetic magnetization, a TI can preserve its gapless states \footnote{R. S. K. Mong, A. M. Essin, and J. E. Moore, Phys. Rev. B 81, 245209 (2010).}. We conduct a systematic study \footnote{S. Ghosh and A. Manchon, arXiv:1609.01174.} on two-dimensional antiferromagnetic TI and find that they are more robust compared to a ferromagnetic TI against impurity scattering. It can facilitate a field like SOT due to the intrinsic spin-orbit coupling and an antidamping SOT via scattering by scalar impurity. Interestingly, a moderate amount of impurity enhances the staggered spin density at the edges resulting in a uniform antidamping torque with the conductance remaining finite. It is, therefore, possible to manipulate the magnetization either by using a pulse \footnote{T. Jungwirth et. al., Nat. Nanotechnol. 11, 231 (2016).} via field like SOT or by a dc current via antidamping SOT.