Quantum Interference Of Spin-dependent In Quantum Dot System

One important characteristic of electron is spin which is used to transferinformation, storage information and processing information. Recently, the reversibilityof the magnetic switch has been achieved using the spin while keeping currentconstant. The study on the novel and marvelous physical characteristics has become aforefront in condensed matter physics, which provides a physical basis for furtherdeveloping electronic and optoelectronic devices. In this thesis, we study the transportproperties in an AB ring embedded in two parallel coupled double quantum dot system,spin dependent Fano effect in parallel coupled four quantum dots system, and thespin-polarized currents and spin accumulation in a three-terminal two quantum dotssystem by means of the non-equilibrium Green’s function method.Firstly, we investigated the electron transport properties in AB interferometerinserted two double-coupled quantum dots with the RSO interaction. The followingobjectives can be achieved:(1) The anti-resonance in conductance spectrum originatesfrom quantum interference between the bonding state and antibonding state;(2) Theposition of anti-resonance of each spin component is always pinned atε=±twhether the RSO interaction is turned on or not.(3) The magnitude ofconductance of each spin component can be manipulated by tuning the RSO interactionstrength. Especially only one spin component electron can be allowed to transportthrough this structure by modulating the strength of RSO interaction properly. Thischaracteristic may be used to design the spin valve devices.Secondly, we study spin dependent Fano effect in parallel coupled four quantumdots system. The coupling strengths between the quantum dots1and3, quantum dot2and4are fixed. When the coupling strength between the quantum dot1and2is verysmall, the characteristics of conductance spectrum is same as that of AB interferometerinserted two double-coupled quantum dots. With the increase of the coupling strength,the ghost Fano peak in conductance spectrum appears due to the quantum interferencebetween multi-paths. When Rashba spin-orbit coupling interaction is considered, theconductance for different spin component can be modulated by Rashba spin-orbit coupling interaction.In addition, the spin polarized current and spin accumulation in a three-terminaltwo quantum dots system has been investigated. We find that with help of the RSOinteraction, the spin polarized currents with opposite direction can be extracted into theleft and right leads in the case ofμ_M> μ_L=μ_Rdue to the quantum interferencebetween different channels. When the relationε=μ_αor ε+U=μ_α(α=L, R)is satisfied, the maximum values of spin polarized current ΔJand the spinaccumulationΔ niappear. The magnitude and direction of polarization can be tunedby adjusting the dots’ levels and the strength of RSO interaction.In short, we systematically investigate the spin polarized transport in coupledquantum dots system based on Rashba spin-orbit coupling interaction. Our aim is tomanipulate spin with all electric method and clarify the influence of the Rashbaspin-orbit coupling interaction, structural parameters on the spin polarized transportproperties. The results we obtained maybe provide a theoreticalbasis for designing spintronics devices.