We investigate the spin-orbit torque exerted on the magnetic moments of the transition-metal impurities Cr, Mn, Fe, and Co, embedded in the surface of the topological insulator Bi2Te3, in response to an electric field and a consequent electrical current flow in the surface. The multiple scattering problem of electrons off impurity atoms is solved by first-principles calculations within the full-potential relativistic Korringa-Kohn-Rostoker (KKR) Green function method, while the spin-orbit torque calculations are carried out by combining the KKR method with the semiclassical Boltzmann transport equation. We analyze the correlation of the spin-orbit torque to the spin accumulation and spin flux in the impurities and unveil the effect of resonant scattering. In addition, we relate the torque to the resistivity and Joule heat production. We predict that the Mn/Bi2Te3 is optimal among the studied systems.
The quasiparticle interference (QPI) technique is a powerful tool that allows to uncover the structure and properties of electronic structure of a material combined with scattering properties of defects at surfaces. Recently, this technique has been pivotal in proving the unique properties of the surface state of topological insulators which manifests itself in the absence of backscattering. Herein, a Green function-based formalism is derived for the ab initio computation of Fourier-transformed QPI images. The efficiency of the new implementation is shown at the examples of QPI that forms around magnetic and nonmagnetic defects at the Bi2Te3 surface. This method allows a deepened understanding of the scattering properties of topologically protected electrons off defects and is a useful tool in the study of quantum materials in the future.
Department of Physics National and Kapodistrian University of Athens University Campus GR-157 84 Zografou, Athens