Itinerant Spin-Dynamics in Structures of Reduced Dimensionality

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In this project we intend to study the spin dynamics and quantum transport in disordered semiconductor quantum wires with spin-orbit coupling using the methods we have developed recently within the project B9 of SFB 508. In particular, we will derive the dependence of the spin relaxation rate and the weak localisation correction to the conductance on the strength and the kind of spin-orbit interaction (linear and cubic Dresselhaus, as well as Rashba coupling), growth direction, width of the quantum wires, mobility and temperature. Furthermore, the result is expected to depend on the smoothness of the transversal confinement of the quantum wires. We are motivated by recent experiments [A1-A7] which report the dimensional reduction of the spin relaxation rate in agreement with our previous results, but are raising new questions, in particular as regards the crossover from diffusive to ballistic wires, and dependence on growth direction and confinement potential. These results call for a nontrivial extension of our previous derivations, which were derived in the diffusive regime.Furthermore, experimental results which were recently interpreted as antilocalisation in magnetic semiconductor quantum wires [A8], require a further extension of the theory in order to be able to calculate the magnetconductivity in these magnetic materials.Motivated by experiments which report a minimal spin relaxation rate at the metal-insulator transition in n-doped GaAs [A9], we will also study the Dyakonov-Perel-spin relaxation in a multifractal state at the Anderson-metal-insulator transition, using an analytical method developed recently