Itinerant Spin Dynamics in Structures of ... - Jacobs University
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Itinerant Spin Dynamics in Structures of ... - Jacobs University

Itinerant Spin Dynamics in Structures of ... - Jacobs University Itinerant Spin Dynamics in Structures of ... - Jacobs University

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11.03.2014 Views

©2011 - Paul Thomas Wenk All rights reserved.

Itinerant Spin Dynamics in Structures of Reduced Dimensionality Abstract In the present thesis results of the study of spin dynamics and quantum transport in disordered semiconductor quantum wires with spin-orbit coupling are presented. Starting from basic spin dynamics we derive the dependence of the weak localization correction to the conductance on the strength and the kind of spin-orbit interaction (linear and cubic Dresselhaus, as well as Rashba coupling), the width of the quantum wires as well as the mobility, temperature and Zeeman term. Furthermore, we exploit the connection found between the microscopic picture given by the Cooperon and the spin diffusion equation to extract the spin relaxation rate which shows the same wire dependencies as the weak localization correction. We also show how the result depends on the smoothness and the direction of the transverse confinement of the quantum wires. In this context we have addressed the question concerning long persisting or even persistent spin states in spintronic devices, presenting the corresponding optimal adjustment of spin orbit couplings of different kind and optimal alignment of the wire direction in semiconductor crystals. Experiments[HSM + 06, HSM + 07, KKN09, LSK + 07, WGZ + 06, SGB + 09] which report the dimensional reduction of the spin relaxation rate in agreement with previous results were raising new questions, in particular as regarding the crossover from diffusive to ballistic wires, which we answer using modified Cooperon equation. In addition, we focus on the intrinsic spin Hall effect, which is only due to spin-orbit coupling. Having shown the basic features with analytical calculations, we solve the spin Hall conductivity in presence of binary and block-distributed impurities (Anderson model). At this we apply the Kernel Polynomial Method, which allows for a finite size analysis of the metal-insulator transition and the calculation of spin Hall conductivity in large systems compared with those addressable with exact diagonalization. iii

©2011 - Paul Thomas Wenk<br />

All rights reserved.

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