半导体量子阱中的自旋轨道耦合及持续自旋螺旋研究

The spin-orbit (SO) coupling, which couples the charge’s angular momentum and its spin, makes the electric control of spin become a reality. In addition, the SO coupling is also the leading source giving rise to a number of emerging novel physical concepts and phenomena in condensed matter physics, including the persistent skyrmion lattice (PRL/2016) and stretchable persistent spin helix (PRX/2017) that we recently found based on the steady-state framework. In this project, we not only aim at a deep extension of our current outcome in the steady-state framework, but also focus on transport properties driven by an electric field applied in the plane of two-dimensional electron gas (2DEG). The research contents are as follows. We first explore the strategies to enhance the stretchability of persistent spin helix. Then, we determine real-space distributions of two-band persistent spin helices in quantum wells with different growth directions and the corresponding stretchability, and investigate potential topological properties of the system. Moreover, we investigate the effect of electron many-body interactions on the SO coupling. As far as the dynamical framework is concerned, we establish the transport properties of persistent skyrmion lattice driven by an electric field in the presence of both intraband and interband SO couplings. Furthermore, by considering topological properties of the skyrmion lattice itself, which usually arise in connection with many-body interactions in chiral magnets, we explore the emerging topological Hall effect and the skyrmion Hall effect in conventional semiconductors. The above research contents, are crucial for achieving the coherent spin control of long time and long distance, and the relevant work is the key for realization of nonballistic spin field-effect transistor and other novel semiconductor spintronic devices harnessing spin manipulation to give new functionalities.

自旋轨道耦合不但使自旋的电调控成为现实，更是主导当前凝聚态物理诸多新概念和新现象的根源，如我们近期在静态图景下首次提出的持续斯格明子晶格（PRL/2016）及可拉伸持续自旋螺旋（PRX/2017）。在此基础上，本项目将更加深入的探讨现有静态图景，并重点研究系统的动态输运性质。研究内容包括：探讨增强持续自旋螺旋“可拉伸度”的方案；分析量子阱不同取向下双子带持续自旋螺旋的分布形式及可拉伸性，揭示其可能的拓扑特性；探讨电子多体效应对自旋轨道耦合的影响；计入带内和带间自旋轨道耦合项，建立持续斯格明子晶格在外场驱动下的动态图像；考虑到斯格明子晶格本身的拓扑结构，研究相应的拓扑霍尔效应及斯格明子霍尔效应。这些工作对于实现长时间和远距离自旋相干调控具有重要意义，也是实现非弹道输运自旋场效应管及其它新型自旋电子器件迫切需要解决的关键问题。

自旋轨道耦合是设计和开发自旋电子器件需要考虑的核心因素。在该项目的支持下，我们围绕自旋轨道耦合及与之相关的持续自旋螺旋、持续斯格明子晶格做了系统研究。确立了纤锌矿受限半导体系统中的自旋轨道耦合性质，得到了适用于量子阱、量子线以及量子点的普适自旋轨道耦合哈密顿量。针对量子三阱，明确了电荷带间转移以及能级交叉与反交叉对自旋调控的影响，实现了对Dresselhaus自旋轨道耦合的灵活调控。基于阶梯量子阱，通过调节内部阶梯势垒的高度，实现了对量子阱中不同子带自旋轨道耦合的选择性调控，揭示了量子阱不同子带自旋轨道耦合特性的关联行为。确定了准二维系统中持续自旋螺旋态的对称性破缺，并在低阶近似下，忽略Cooperon三重态散射模式的耦合以及不同朗道能级之间的耦合，推导出了具有闭合形式的弱局域化磁电导解析表达式。研究了界面效应诱导的Dresselhaus自旋轨道耦合，发现其强度与常规项相比，为理论结合实验确定准确的体Dresselhaus系数提供了支撑。另外，亦将相关方法推广到新型二维材料中，研究了其中的自旋与能谷物性，如激子和带电激子的自旋、能谷动力学行为等。相关工作对于实现长时间和远距离自旋、能谷相干调控具有重要意义，是在二维扩散系统中实现非弹道输运自旋场效应管等新型自旋电子器件迫切需要解决的关键问题。