This thesis presents a study of the electron spin and transport properties in low-dimensional systems. Three issues are analyzed in this thesis. First, I construct a model to analyze entanglement generation in a quantum dot sys-tem. Second, I investigate electron spin relaxation and decoherence in quantum dots affected by hyperfine interactions. Third, I explain resistance anomaly for nanowires with very small radii....[ Read more ]

This thesis presents a study of the electron spin and transport properties in low-dimensional systems. Three issues are analyzed in this thesis. First, I construct a model to analyze entanglement generation in a quantum dot sys-tem. Second, I investigate electron spin relaxation and decoherence in quantum dots affected by hyperfine interactions. Third, I explain resistance anomaly for nanowires with very small radii.

The generation of entanglements is very important in the improvement of quantum information and quantum computation. In this thesis, I construct a model using a two-quantum-dot system to generate spatially separated, entan-gled electron pairs. The spatial separation is guaranteed by the large on-site Coulomb interaction of electrons. I discuss the efficiency of our model based on calculations. The total generation time for a couple of entangled electrons is investigated. I also compare our model with other proposals presented and find that our model is more applicable and requires less energy properties of quantum dots and leads.

Spin relaxation and decoherence are important issues in spintronics. They are included in our entanglement generation model. I investigate spin relaxation and spin decoherence in quantum dots. The main effect of spin relaxation and spin decoherence is a hyperfine interaction with nuclear spins in quantum dots. In our discussion, we model the hyperfine interaction as a stochastic process. I show that it is necessary to introduce the ensemble spin relaxation time, T₁*, to describe spin relaxation in quantum dots. We also compare the spin relaxation time, T₁, and the decoherence time, T₂, in this system.

In the last part of this thesis, we illustrate the resistance anomaly in nanowires observed recently in experiments. The resistance anomaly occurs when a nanowire has a very small radius but a long length (diffusive region) and Ohm's law is broken. We think that the anomaly can be understood when all the scatterers in the nanowire contribute to the resistance, and the lower radius will reduce the number of scatterers to reduce the resistance. We calculate the transition radius and compare it with experimental results.