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978-3-8439-1325-6, Reihe Physik
Contributions to the Theory of Spin-Correlations in Electron Gases With Spin-Orbit Coupling
249 Seiten, Dissertation Technische Universität Kaiserslautern (2013), Softcover, A5
This thesis contains a theoretical investigation of the response of electron gases, as they are realized in n-doped GaAs-based semiconductors to external electric and/or magnetic fields. The response functions considered here underlie Raman scattering and spin-noise spectroscopy of semiconductors. Technically, the analysis is done within the equation-of-motion approach of Green’s function theory. Deriving the 2-particle correlations allows to determine the dielectric function and the magnetic susceptibility tensor. The influence on the response functions of the different spin-orbit coupling effects is of particular interest. In combination with carrierimpurity interaction, spin-orbit coupling leads to the D’yakonov-Perel’ spin-relaxation. Therefore, carrierimpurity interaction needs to be included in a realistic calculation of spin-dependent response functions. Part of this thesis is devoted to an analysis of the “fingerprints” of the spin-orbit coupling in the free response functions. In the next step, the Coulomb interaction between electrons in the conduction band is taken into account. This allows to describe collective charge and spin excitations of the electron plasma. Of particular interest is the influence of the spin-orbit coupling on the quasiparticle resonance conditions and their dispersions including external fields.
The presentation of numerical results starts with the dielectric function in the random phase approximation (RPA). An analysis of the influence of spin-orbit coupling on the single-particle spectra and on the collective excitations, i.e., the plasmon and the magnetoplasmon, is given. In this thesis, a version of the Tjablikov decoupling in regard of the response function is developed that can be applied including spin-orbit coupling. It is used to derive the relevant equations of motion in an analytically closed manner for the magnetic susceptibility, which are then numerically evaluated. The effects of spin precession in external and internal magnetic fields on the longitudinal magnetic susceptibility are studied. Then the transverse magnetic susceptibility is calculated. It is of major interest for the description of spin relaxation and spin fluctuation processes in solid state physics, but its microscopic calculation at this level has not been done before. The collective spin resonance are studied for different spin-orbit coupling strengths and external fields.