Persistent Spin Current For A Rashba Spin-Orbit Coupling Quantum Wire

Spintronics (or spin-electronics), is a science of using the spin degrees of freedom of electron in sold-state systems for information storage, processing and transport. It is also an active branch of nanotronics. Spintronics based on the electron spin-orbit coupling (SOC) in nonmagnetic semiconductor heterostructures has become very popular area of research in the growing field of spintronics recently. The ability to manipulate electron spin and spin current without external magnetic fields in mesoscopic system is of critical importance for the design of new quantum bit and quantum storage devices. The mesoscopic systems, such as quantum wire and quantum dot, will be very important parts of the quantum nanocircuit. Therefore, it is interesting to investigate the effect of spin-orbit coupling on the spin current of quantum wire for both basic physics understanding and high technological applications.In this thesis, using a recently developed proper definition of spin current, we study the low temperature electron spin current for a weak Rashba SOC semiconductor quantum wire in the framework of effective-mass free electron model. We have found some interesting results for spin current in this system.The thesis consists of five chapters. In chapter one and chapter two, we briefly introduce and discuss the two types of SOC with their physical origin and their influence on the electron transport properties, which includes spin accumulation, spin precession, spin-polarized transport and spin current as well as spin Hall effect.In chapter three, we theoretically study the low temperature persistent electron spin current in a semiconductor quantum wire with weak Rashba SOC. The influence of both the Rashba SOC strength and the confining potential on the spin current is treated analytically by a recently developed proper definition for spin current within effective-mass free-electron approximation. Through analytical analysis and numerical examples, we find that the elements of spin current in this system shows different sensitivity to Rashba SOC strength. Our result may imply a simple method for the design of a new quantum bit and storage device without involving any magnetic materials or magnetic fields.In chapter four we study the spin current at higher energy level with a large quantum number, and we find it shows a correspondence characteristic accord with the classical theory. Chapter five gives a summary of the work and a outlook of this topic.