Spin-Bias-Induced Spin Transport In Quantum Dot Device

Semiconductor quantum dot (QD) is a quasi-zero-dimensional mesoscopic structure, which presents discrete electron energy spectrum and strong electron interaction. Because of such electronic characteristics, a single QD is viewed as an artificial atom. Accordingly, a structure consisting of several coupled QDs confines electrons in a way as an artificial molecule. In contrast to a single QD, multiple QD structures possess more structural parameters to tune their electronic transport properties. Therefore, the investigations on the multiple QD structures are the current focus in the field of mesoscopic physics. In this thesis we report our theoretical investigations about the electron and spin transport through parallel double QD structure, by means of non-equilibrium Green function technique, thereby, some interesting results are obtained. Below we outline our works briefly from two aspects:On the one hand, we studied the spin-polarized electron transport through a double quantum-dot (QD) Aharonov-Bohm-Fano (ABF) interferometer, by considering the spin bias in the source electrode. It is found that the spin bias, via modulating the electron transmission in the nonresonant channel, drives apparent charge and spin currents in the drain electrode. Simultaneously, in the resonant-channel QD there appears striking spin-bias-induce spin accumulation, the characteristics of which are tightly dependent on the strengths of intradot Coulomb interactions. Furthermore, when a charge bias is introduced between the source and drain electrodes,the currents in the drain electrode and the spin accumulation in the resonant-channel QD can be efficiently manipulated by the change of the charge bias amplitude, including the changes of the direction and amplitude of both the currents and spin accumulation.On the other hand, electronic transport through a triple-quantum-dot ring with three terminals is theoretically studied. By introducing local Rashba spin-orbit interaction on an individual quantum dot, we find that the spin bias in one terminal drives apparent charge currents in the other terminals, accompanied by the similar amplitude and opposite direction of them. This menas that in this structure the spin bias can be measured by virture of the charge current properties. Meanwhile, the spin transport induced by the spin bias is notable. When a magnetic flux is applied through this ring, we see its nontrivial role in the manipulation of the charge and spin transport. With the obtained result, we also propose this structure to be a prototype of a charge and spin current rectifier.