Low-dimensional mesoscopic electron transport system in the spin

Title: Low-dimensional mesoscopic electron transport system in the spin Author: Ye Chengzhi Degree-granting unit: Shanxi University Keywords: superlattice;; quantum dots;; spin-polarized transport;; polarization;; spin current Summary: And spin-dependent quantum transport in spintronics research field is currently a hot topic. This paper briefly reviews the semiconductor quantum wells, superlattices and quantum dots after the concept of quantum transport in several commonly used research methods briefly described, such as the Landauer-Buttiker formula, the transfer matrix, scattering matrix and non- equilibrium Green's function method. Then, the electrons in semiconductor double-barrier structure, the more potential well semiconductor superlattice, double AB interferometer, double quantum neodymium magnets dots formed by the four-terminal AB interferometer in the spin-dependent transport properties were studied. First, the use of the effective mass approximation, Floquet theory and transfer matrix method to study the external oscillating field and spin-orbit coupling under the influence of electrons through asymmetric double-barrier structure of the semiconductor transport properties. The results show that Dresselhaus spin-orbit coupling eliminates the spin degeneracy, resulting in conductivity spin splitting. With the oscillating field oscillation amplitude increases, the emergence of multi-photon process, the number of resonance peaks and the two adjacent resonance peaks by distance between the external oscillating field amplitude and frequency control. In addition, the potential well is narrow, the oscillating field of the oscillation amplitude is small, can be modulated high-spin-polarized photon electronic transmission, the use of this nature can expect to achieve a tunable spin filter device. Secondly, the use of transfer matrix method to study the potential well region contains Dresselhaus spin-orbit coupling, the electronic potential well by many semiconductor superlattice tunneling nature. With single-and double-well potential well compared to more potential well semiconductor superlattice structure enhances the transmission electron spin polarization. Spin-orbit coupling eliminates the spin degeneracy, leading to low incident energy region of the full spin splitting of electronic microstrip, resulting in a larger energy window to achieve 100% polarization of electronic transmission, which can serve to achieve self- an effective spin filter program. In addition, we found that electrons from the potential well above the potential well formed by the n-semiconductor superlattice structure, a resonance peak splitting in microstrip rules as follows: n n-1 heavy weight split or split, it depends on the potential well width and barrier thickness. The rules and electronic barrier formed by n-semiconductor superlattice structure of the resonance peak splitting rules are different. Next, the use of non-equilibrium Green's http://www.chinamagnets.biz/Neodymium/Ball-Neodymium-Magnets.php function method to study the double AB interferometer RSOI caused by Andreev reflection of spin-polarized nature of the flow. Spin polarization can be adjusted by AB flux φ, RSOI strength, and the coupling between two quantum dots to control the intensity t_c. Regardless of whether the coupling between two quantum dots, we can get the full flow of spin-polarized Andreev reflection, but only if there is no coupling between two quantum dots, the full spin-polarized Andreev reflection is the maximum flow of. Finally, the study of the double quantum dots formed by the four-terminal AB interferometer transport properties, taking into account the ferromagnetic electrode and the RSOI on the impact of transport. Based on the normal transmission and cross Andreev reflection, the right electrode can collect electrons and holes spin up, spin down electrons and holes. By adjusting the ferromagnetic electrode polarization, AB flux, RSOI-induced phase φ_R other parameters, this system will make a spin component of the particle is not transmitted, while the other collected from the electronic and spin component an equal number of holes, resulting in no net charge flow of spin current. Therefore, this model can be used as a spin injector. Degree Year: 2009