The Influence Of Spin-Orbit Coupling On Electron Transport Properties For An Semiconductor 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 in nonmagnetic semiconductor heterostructures has become very hot area of research in the growing field of spintronics recently. The ability to manipulate electron spin without external magnetic fields in mesoscopic system is of critical importance for the design of spin-injection devices and spin filters. The mesoscopic system, 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 Rashba spin-orbit coupling (SOC) on the transport properties of quantum wire for both basic physics understanding and high technological applications.In this thesis, using the scattering matrix method within Landauer-Büttiker frame, we study the low temperature electron transport properties for a weak SOC semiconductor quantum wire connected to two normal metal electrodes (leads) in the framework of effective-mass free electron model. We have found some interesting results for this system.The thesis consists of four chapters. In chapter one and chapter two, we briefly introduce and discuss the two types of SOC with their physical origin and the 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 electron transport properties of a weak SOC semiconductor quantum wire connected nonadiabatically to two electrode leads without SOC. the influence of both the wire-lead connection and the Rashba SOC on the electron transport is treated analytically by means of scattering matrix within effective-mass free-electron approximation. Through analytical analysis and numerical examples, we find that the system shows some fractional quantum conductance behavior, and for some particular wire width there exists a pure spin polarized current. Our result may imply a simple method for the design of a spin filter without involving any magnetic materials or magnetic fields.Chapter four gives a summary of the work and a outlook of this topic.