Antiferromagnetic helix as an efficient spin polarizer: Interplay between electric field and higher-order hopping

We report a spin filtration operation considering an antiferromagnetic helix system, possessing zero net magnetization. Common wisdom suggests that for such a system, a spin-polarized current is no longer available from a beam of unpolarized electrons. But once we apply an electric field perpendicular to the helix axis, a large separation between up-and down-spin energy channels takes place, which yields a high degree of spin polarization. Employing a tight-binding framework to illustrate the antiferromagnetic helix, we compute spin filtration efficiency by determining spin-selective currents using Landauer-Buttiker formalism. Geometrical conformation plays an important role in spin-channel separation, and here we critically investigate the effects of short-range and long-range hoppings of electrons in the presence of the electric field. We find that the filtration performance gets improved with increasing the range of hopping of electrons. Moreover, the phase of spin polarization can be altered selectively by changing the strength and direction of the electric field, and also by regulating the physical parameters that describe the antiferromagnetic helix. Finally, we explore the specific role of dephasing to make the system more realistic and to make the present communication a self-contained one. Our analysis may provide a route of getting conformation-dependent spin polarization possessing longer range hopping of electrons, and can be generalized further to different kinds of other fascinating antiferromagnetic systems.

Automated summary

We report a spin filtration operation in an antiferromagnetic helix system, where a high degree of spin polarization can be achieved by applying an electric field perpendicular to the helix axis. The separation between up-and down-spin energy channels is influenced by the geometrical conformation, and the filtration performance is improved with increasing the range of hopping of electrons. The phase of spin polarization can be selectively altered by changing the strength and direction of the electric field, as well as regulating the physical parameters of the helix.