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

Chapter 4
Direction Dependence of Spin
Relaxation and Diffusive-Ballistic
Crossover
4.1 Introduction
In Chapter3 it was shown how the spin relaxes in a quasi 1D electron system in
a quantum well grown in the [001] direction, depending on the width of the wire, where
the normal of the boundary was pointing in the [010] direction. In a system with only
Rashba SOC or linear Dresselhaus SOC in a (111) quantum well it is clear from the vector
fields plotted in Fig.2.2 that a rotation in the plain should not effect the physics,
i.e. the minimal spin relaxation rate will not reduce. The linear Rashba SOC does
not depend on the growth direction at all. It is already known that on the other hand
in a (001) 2D system with both BIA[Dre55] and SIA[BR84] we get an anisotropic spinrelaxation.[KRW03,
CWd07, WJW10] This has also been studied numerically in quasi-1D
GaAs wires[LLK + 10]. In this Chapter, Sec.4.2, we present analytical results concerning
this anisotropy for the 2D case as well as the case of quantum wire with spin and charge
conserving boundaries. As in the previous chapter, also here we focus on materials where
the dominant mechanism for spin relaxation is governed by the DP spin relaxation.
Furthermore we extend our analysis to other growth directions, Sec.4.3: Searching for long
spin decoherence times at room temperature, the (110) quantum wire attracted attention.
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