量子点与超导电极耦合的多端系统中自旋输运问题的研究

The spin-polarized quantum transport, as a matter of fact, is one of the theoretic foundation of the spintronic devices. How to realize completely spin-polarized current or pure spin-current is always the center matter of spin-polarized quantum transport. In this project, we will investigate theoretically how to realize the pure spin-current injector in the experiment by means of electrons and holes in the multiterminal system formed by semiconductor quantum dots contacted to the superconductor lead. (We have already began the realization of this kind of pure spin-current without net charge current, and have made some progress. But the results is hard to be realized in the experiment. In this project, we will continue this investigation to scheme out the pure spin-current injector which can be realized in experiment easily). In this project, we will investigate the spin accumulation in the multiterminal system formed by semiconductor quantum dots contacted to the superconductor lead. In this project, we will also derive the expression of shot noise to the case when Andreev-reflection occuring, and investigate the shot noise in the multiterminal system formed by semiconductor quantum dots contacted to the superconductor lead. By analyzing the shot noise, the microcosmic mechanism about the spin-polarized transport can be revealed. The results in this project should be useful to the design of spintronic devices.

自旋极化输运是自旋电子学的理论基础之一。如何得到完全自旋极化的电流或者纯自旋流一直是自旋极化输运的中心问题。本项目将从理论上研究在半导体量子点与超导电极耦合的多端系统中，如何利用电子和空穴来实现实验上容易实现的纯自旋注入器。（申请人在该方面已经取得了一些研究进展，但所得结果在实验中实现是有困难的。本项目将继续此方面的研究，进一步设计出实验上容易实现的纯自旋流注入器）。本项目还将研究在半导体量子点与超导电极耦合的多端系统中的自旋累积现象。我们将推导出有Andreev反射存在时的shot noise的表达式，在半导体量子点与超导电极耦合的多端系统中，研究电流噪声谱。通过分析电流噪声谱，获得更多关于自旋极化输运的微观机制信息。研究成果可以为自旋电子器件的设计提供理论依据。

自旋极化输运是自旋电子学的理论基础之一。本项目主要从理论上研究了半导体量子点与超导电极耦合的多端系统中自旋相关的输运问题。本项目研究了半导体量子点与超导电极耦合的多端系统中的Andreev反射流、电子占据数、自旋累积、Andreev反射电导、散粒噪声等输运问题，研究了铁磁电极、Rashba自旋轨道相互作用、自旋翻转散射、库仑相互作用等对自旋相关输运问题的影响。在所研究的半导体量子点与超导电极耦合的多端系统中可以得到完全自旋极化的Andreev反射流、完全自旋极化的量子点等现象。本项目还研究了单层和双层石墨烯中不同势垒调制下的电子隧穿性质，研究了Dresselhaus自旋轨道耦合和两种振荡场调制下半导体量子阱的自旋极化共振隧穿性质。本项目的研究内容将会为相关自旋电子器件的设计提供理论依据。