Influence Of The Spin-Orbit Coupling On The Transport Properties Of Coupled-Quantum-Dot System

The purpose of spintronics is to manipulate the spin degree of freedom instead of (or together with) the charge degree of freedom in solid-state system. In this multidisciplinary field, people try to develop spintronic devices to substitute the traditional electronic devices. The three of the most important issues in this field are: (1) prolonging the spin decoherence time, (2) efficient generating spin polarization and (3) measurement of the spin polarization.In this dissertation, by means of the non-equilibrium Green'function and the slave boson mean-field approximation, we investigate the spin accumulation, spin-polarizition transport properties and pure spin currents in double quantum dots (DQDs), in which the Rashba spin-orbit(RSO) interaction exists, as well as the Kondo-assisted transport in Kondo regime. We investigate the influences of the quantum dot level, magnetic flux, the bias voltage, and the RSO interaction on the spin polarized transport properties of coupled-quantum-dot system theoretically and get some significant results.Firstly, we investigate the spin-dependent Fano effect through parallel-coupled DQDs connected to two electrodes symmetrically. We found that the base cause of manipulating the Fano line shape in the conductance spectra is that the resonace channel, non-resonace channel, and interference between these two channels can be tuned by RSO interaction. The RSO interaction and the magnetic flux play an essential role in spin-resolved transport through the system in interacting regime. For the case with ? = 0, the spin-independent Fano resonance can be controlled by the strength of the RSO interaction; when the magnetic flux is switched on, the Fano line shape of each spin component can be modulated by the value of ? R. Moreover, the intradot electron-electron interaction is taken into account, the conductance spectra of each spin component is divided into two sections. One centered at the bonding state and antibonding state, the other at their Coulomb blockade counterparts.Secondly, we investigated the spin accumulation of Aharonov-Bohm (AB) interferometer, in which an interacting quantum dot (QD) is inserted in each arm. The spin accumulation in QD emerges in presence of RSO interaction even though no magnetic materials and magnetic field. It is found that the following objectives can be achieved: (1) the magnitude and direction of the spin accumulation in the QD can be controlled and tuned by the gate voltage or the bias; (2) the spin accumulation in two dots is sensitive to the strength of RSO interaction andΔnias function of ? Rexhibits a periodic function with the period of 2π; (3) the position of the maximum of the spin accumulation can be modulated by the intradot level , Coulomb interaction and the bias together.Thirdly, the spin–polarized current through a three-terminal parallel-coupled DQDs device has been investigated by taking account of both the RSO interaction and intradot Coulomb interaction. The spin-dependent current formulas and relevant Green functions are obtained within the framework of the Hartree-Fock approximation. We find that by properly choosing the strength of RSO interaction and bias voltages, the spin-up and spin-down currents can be extracted into the left and right leads, respectively. In particular, a pure spin current, whose the magnitude and direction can be tuned by arranging the bias voltage applied between the three leads, can be driven out from the middle lead.Finally, by means of the salve-boson mean field approximation, we study the transport properties of DQDs in Kondo regime with RSO interaction. We show that the transmission probability, the local density of states, and linear conductance of each spin electron become different by tuning RSO interaction strength with certain magnetic flux. We find that by properly choosing the strength of RSO interaction,one spin component is allowed to pass the structure, but the other spin component is forbidded. This property can be used to designe the spin valve.In conclusion,we systematically investigate the spin polarized transport properties through double quantum dots system, especially emphasis on the influcences of the electronic methods on the manipulation of spin. It is clarified how the Rashba spin-orbit interaction, Coulomb interaction and structure parameters change the spin polarized transport properties. The results, we obtained, can be applied to design of spintronics devices and quantum computation.