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

24 Chapter 2: Spin Dynamics: Overview and Analysis of 2D Systems field dependence due to the weak Pauli-paramagnetism. In the next chapter we will also analyze the effect of a Zeeman term on the crossover from weak localization to weak antilocalization. As we will see, this crossover can be controlled by spin relaxation rate.

Chapter 3 WL/WAL Crossover and Spin Relaxation in Confined Systems 3.1 Introduction To build spin based devices which rely on coherent spin precession of conduction electrons[DD90, ZFD04], as presented in the introduction of this work, it has to be analyzed under which conditions, such as wire geometry, type and intensity of SOC, impurity density etc., spin relaxation rate can be minimized. We have shown in Sec.2.4 that if electron momentum is randomized due to disorder, SO interaction is expected to result not only in a spin precession but in randomization of the electron spin with rate 1/τ s .[DP72] In the following we focus on the D’yakonov-Perel’ spin relaxation mechanism. 3.1.1 One-Dimensional Wires In one-dimensional wires, whose width W is of the order of the Fermi wave length λ F , impurities can only reverse the momentum p → −p. Therefore, the spin-orbit field can only change its sign, when a scattering from impurities occurs. B SO (p) → B SO (−p) = −B SO (p). Therefore, the precession axis and the amplitude of the spin-orbit field does not change, reversing only the spin precession, so that the D’yakonov-Perel’-spin relaxation is absent in one-dimensional wires[KK00, MFA02]. In an external magnetic field, the precession around the magnetic field axis, due to the Zeeman-interaction is competing with the spin-orbit field, however. Then, as the electrons are scattered from impurities, both the 25

24 Chapter 2: <strong>Sp<strong>in</strong></strong> <strong>Dynamics</strong>: Overview and Analysis <strong>of</strong> 2D Systems<br />

field dependence due to the weak Pauli-paramagnetism.<br />

In the next chapter we will also analyze the effect <strong>of</strong> a Zeeman term on the crossover from<br />

weak localization to weak antilocalization. As we will see, this crossover can be controlled<br />

by sp<strong>in</strong> relaxation rate.

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