Electronic spin and valley degrees of freedom - based novel quantum devices

电子除了是带电粒子外，还有一个额外的量子自由度，即它们的自旋。在某些材料中，电子也有谷自由度，这与它们的动量有关。自旋电子学和最近的谷电子学是固态科学和工程的新兴领域。他们的广泛目标是利用载流子的自旋/谷自由度来实现依赖于自旋/谷电流的创建、操纵和检测的新型电子设备。如果成功，这种操作也可能影响量子计算的更奇特的领域，因为自旋/谷是在量子计算机中记录量子信息的候选者。本文提出的项目重点是研究层状半导体结构中清洁载流子系统的弹道输运。目标是演示和描述一些新颖的原型电子设备，其操作依赖于自旋和/或谷自由度的操纵。这些项目还包含了全面的教育成分，包括对研究生和本科生在薄膜半导体结构的制造、表征和物理方面的培训。拓展活动包括K-12的示范和电磁学教师培训项目。本文提出的项目旨在研究调制掺杂半导体中清洁二维载流子系统的弹道输运。目标是演示和表征一些设备，其操作依赖于自旋和/或谷自由度的操纵。这些包括自旋干涉装置、自旋滤波器和谷滤波器。该器件将主要基于两种不同的载流子系统：(1)GaAs量子阱中的二维空穴系统，具有强且可调谐的自旋轨道相互作用；(2)AlAs量子阱中的二维电子系统，其中电子占据具有门和/或应变可调谐密度的导带谷，并且具有较大的朗德有效g因子，因此它们易于自旋极化。本提案中描述的所有项目将涉及使用现代晶体生长和光刻技术制造各种器件，以及传输测量。这些项目将有助于从根本上理解半导体结构中的弹道输运。虽然所提出的结构将主要在相对较低的温度下运行，但它们将作为原型来演示对自旋电子学/谷电子学和量子计算等新兴领域的进步至关重要的原理验证概念。这些项目也可能导致不可预见的设备概念的发展。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Electrons, besides being charged particles, have an extra, quantum degree of freedom, namely their spin. In certain materials, electrons also have a valley degree of freedom, which is related to their momentum. Spintronics and, more recently, valleytronics, are emerging areas in solid-state science and engineering. Their broad goal is to utilize carriers' spin/valley degrees of freedom to realize novel electronic devices that rely on the creation, manipulation, and detection of spin/valley currents. If successful, such manipulation could also impact the even more exotic field of quantum computing, as spin/valley are candidates for registering the quantum bit of information in quantum computers. The focus of the projects proposed here is to study ballistic transport in clean carrier systems in layered semiconductor structures. The goal is to demonstrate and characterize a number of novel, prototype, electronic devices whose operation relies on the manipulation of spin and/or valley degrees of freedom. The projects also incorporates comprehensive educational component, including training of graduate and undergraduate students in fabrication, characterization, and physics of thin-film semiconductor structures. Outreach activities involve K-12 demonstrations and teacher training programs in electricity and magnetism.The projects proposed here are aimed at studies of ballistic transport in clean, two-dimensional carrier systems in modulation-doped semiconductors. The goal is to demonstrate and characterize a number of devices whose operation relies on the manipulation of spin and/or valley degrees of freedom. These include a spin-interference device, a spin-filter, and a valley-filter. The devices will be based mainly on two different carrier systems: (1) two-dimensional hole system in GaAs quantum wells which possesses a strong and tunable spin-orbit interaction, and (2) two-dimensional electron system in AlAs quantum wells where the electrons occupy conduction band valleys with gate- and/or strain-tunable densities, and also have a large Lande effective g-factor so that they can be easily spin-polarized. All the projects described in this proposal will involve fabrication of various devices using modern crystal growth and lithography techniques, and transport measurements. The projects will contribute to the fundamental understanding of the ballistic transport in semiconductor structures. While the proposed structures would operate mainly at relatively low temperatures, they will serve as prototypes to demonstrate proof-of-principle concepts that are essential for advances in the emerging fields of spintronics/valleytronics and quantum computing. The projects can also lead to the development of unforeseen device concepts.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.