Current-induced spin polarization in chiral tellurium: a first-principles quantum transport study

Te is a naturally p-doped semiconductor with a chiral structure, where an electrical current causes the conduction electrons to become spin-polarized parallel to the transport direction. In this paper, we present a comprehensive theoretical study of this effect, named current-induced spin polarization (CISP), by employing density functional theory (DFT) combined with the nonequilibrium Green's function (NEGF) technique for quantum transport. CISP can be quantitatively described in terms of the nonequilibrium spin density, which we show to be localized around the atoms. We then compute the atomic magnetic moments as a function of doping and electronic temperature, obtaining results overall consistent with those of previous theoretical studies. Beyond that, our DFT + NEGF calculations show that CISP also leads to a spin current, which is found to be quite a large fraction of the charge current, indicating that Te can be an efficient material for spin transport. We further predict that the resistance along a ballistic Te wire changes when an external magnetic field is applied parallel or antiparallel to the direction of the charge current. The computed magnetoresistance ratio is, however, quite small (similar to 0.025%). Finally, we conclude by arguing that CISP, as treated within the DFT + NEGF framework, coincides with the phenomenon called chiral-induced spin selectivity, recently reported in several nanojunctions.