  We study spin-orbit torques and charge pumping in magnetic quasi-one
dimensional zigzag nanoribbons with hexagonal lattice, in the presence of large
intrinsic spin-orbit coupling. Such a system experiences topological phase
transition from a trivial band insulator to a quantum spin Hall insulator
either by tuning the magnetization direction or the intrinsic spin-orbit
coupling. We find that spin-charge conversion efficiency (i.e. spin-orbit
torque and charge pumping) is dramatically enhanced at the topological
transition, displaying a substantial angular anisotropy.
