Spin Transport In Quasi-one Dimension Quantum Structure

Spintronics is an emerging field that involves the study of active control and manipulation of spin degrees of freedom in solid-state systems. Spin transport in quasi-one dimension mesoscopics system is one of hot topics of spintronics. In this thesis, we study spin transport in quantum wire and graphene nanoribbon based on Green's function. The aim is to explore an effective and efficient way to control electron spin, and to supply physical model and theoretical validity in designing spintronics devices with excellent properties.The paper is organized as follow. In chapter one, some typical mesoscopic system, quantum phenomena and spintronics devices are introduced.The lattice Green's function is introduced in chapter two, which includes recursive Green's function and total Green's function. These methods can be used to deal with magnetic field, electric field or all kinds of quasi-one dimension system with different geometry.In chapter three, we study spin transport in double bend quantum wire. It is found that a notable spin polarization can be achieved in a broad energy range when magnetic field and Rashba spin-orbit coupling only exist in the intersection of two quantum wires. The amplitude of spin polarization can be tuned from 0 to 100% by adjusting RSOC or magnetic field. The effect of geometric size on the spin polarization is discussed.The spin transport in T-type graphene nanoribbon is studied. The result show that there exist many dips in spin conductance. The dips near to the Fermi energy are originated from the broken edge state. The others dips are caused by the quasi-bound state. These dip can be controlled by the external potential and the spin polarization is changed. In addition, the height of stub versus conductance is studied.In summary, a final conclusion is drawn for all the results obtained and the conception of future investigation is explicitly described.