Spin accumulation from nonequilibrium first principles methods

For the technologically relevant spin Hall effect, most theoretical approaches rely on the evaluation of the spin-conductivity tensor. In contrast, for most experimental configurations the generation of spin accumulation at interfaces and surfaces is the relevant quantity. Here, we directly calculate the accumulation of spins due to the spin Hall effect at the surface of a thin metallic layer, making quantitative predictions for different materials. Two distinct limits are considered, both relying on a fully relativistic Korringa-Kohn-Rostoker density functional theory method. In the semiclassical approach, we use the Boltzmann transport formalism and compare it directly with a fully quantum mechanical nonequilibrium Keldysh formalism. Restricting the calculations to the spin-Hall-induced, odd-in-spatial-inversion, contribution in the limit of the relaxation time approximation, we find good agreement between the two methods, where deviations can be attributed to the complexity of Fermi surfaces. Finally, we compare our results with experimental values of the spin accumulation at surfaces as well as the Hall angle and find good agreement for the trend across the considered elements.

Automated summary

This study focuses on the calculation of spin accumulation at the surface of a thin metallic layer and makes quantitative predictions for different materials. By comparing semiclassical and fully quantum mechanical methods, it is found that the two methods agree well in the limit of the relaxation time approximation, with deviations attributed to the complexity of Fermi surfaces. Results are compared with experimental values, showing good agreement in the trend across the considered elements.