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

Abstract

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 by employing density functional theory (DFT) combined with the non-equilibrium Green's functions (NEGF) technique for quantum transport. We suggest that the spin polarization can quantitatively be estimated in terms of two complementary quantities, namely the non-equilibrium magnetic moments and the spin current density. The calculated magnetic moments are directly compared with the values from previous theoretical studies obtaining overall consistent results. On the other hand, the inspection of the spin current density provides insights of the magnetotransport properties of the material. Specifically, we predict that the resistance along a Te wire changes when an external magnetic field is applied parallel or antiparallel to the charge current direction. The computed magnetoresistance is however quite small (~ 0.025%). Finally, we show that the description of the current-induced spin polarization in terms of the spin current establishes a straightforward connection with the phenomenon called chiral-induced spin selectivity, recently observed in several nano-junctions.