Effect of spin-orbit scattering on transport properties of low-dimensional dilute alloys

Heers, Swantje

Dissertation / PhD Thesis/Book

Effect of spin-orbit scattering on transport properties of low-dimensional dilute alloys

Heers, S. (Corresponding author)FZJ*

2011
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich
ISBN: 978-3-89336-747-4

Jülich : Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag, Schriften des Forschungszentrums Jülich. Schlüsseltechnologien / Key Technologies 31, VIII, 216 S. (2011) = RWTH Aachen, Diss., 2011

Please use a persistent id in citations: http://hdl.handle.net/2128/4523

Abstract: The scoppe of this thesis is to gain insight, by means of $\textit{ab initio}$-calculations, into the physics of monumentum and spin relaxation phenomena induced by electron scattering at impurities and defects in the noble metals copper, silver and gold. The main results are subdivided in three parts. In the first part, momentum- and spin-relaxation times due to scattering at $\textit{3d, 4sp,4d, 5sp, 5d}$ adn $\textit{6sp}$ impurities in copper and gold fcc bulk are invetigated. The inversion symmetry of the crystls leads to a two-fold degeneracy of all states on the Fermi surfae, adn therefore spin relaxaation is dominated by the elliott-Yafet mechanism as well as the spin-orbit coupling of the impurity. For impurities in gold , we calculate much shorter spin-relaxation times than in copper because of the stronger spin-orbit coupling of the fold host. Furthermore, we have found important qualitative differences between the relaxation times obtained for the $\textit{d-}$ and the $\textit{sp-}$impurities. As scattering at $\textit{d-}$impurities is resonant, the electrons spend much more time at the impurity sites than in the case of the $\textit{sp-}$impurities; therefore, they are much longer exhibited to the spin-orbit coupling of the impurity. This results in considerably shorter spin-relaxation times, even if the momentum scattering rates are in the same order of magnitude. Finally, the investigation of interference of scattering processes at impurity dimers reveals that relevant differences to the independent-impurity approximation appear only for strong $\textit{d-}$scatterer, palced at nearest neighbouringsites. in the second part we investigate the reduction of spin-conservng surface-state lifetimes induced by adatom- and impurity-scattering on the (111) surfaces of copper, silver and gold films with different thickness. We have found strong qualitative differences in the lifetimes when comparing the results for adatoms to those of impurities in the first and second layer. The trends for the latter ones are similar to those calculated in bulk in the first part of the thesis. In the third part, we investigate spin-orbit induced effects on thin (001) and (111) copper and gold films with focus on spin-relaxation mechanisms. We consider both symmetric and asymmetric systems, where the asymmetry of the latter ones is created by covering one side of the film with one layer of Zn. For the symmetric films, spin-mixing parameters and momentum- and spin-relaxation times due to scattering at self-adatoms are calculated. Whereas the largest spin-mixing in (111) films has been obtained for the surface states, on the Fermi surfaces of the (001) films spin hot spots occur, which are caused by anticrossings of bands and lead to locally very high spin mixing.

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