Experimental Study of the RKKY Interaction in Multi-Quantum-Dot Systems

*非技术抽象*自旋，顾名思义，是描述电子角动量(就像它们在旋转一样)及其相关磁性的基本性质。虽然现代电子学主要使用电子的电荷来编码信息，但电子自旋也在为我们工作，特别是在硬盘驱动器、信用卡条带和任何其他磁性存储介质中。然而，Spin提供了一种更强大的应用--一种尚未出现在任何技术中的应用，但该理论表明，通过利用量子力学定律，可以在计算和通信方面带来革命性的改进。该项目旨在通过实验研究有关自旋取向的信息是如何以一种内在的量子力学方式在电子之间传递的。该项目不是研究自然环境中的电子，例如在金属中(这很难探测和控制)，而是将用被称为量子点的纳米级半导体设备制造人工电子系统，从而对单个电子进行更好的控制。在量子点中，自旋可以通过转动旋钮来耦合和解耦，就像在晶体管中一样。通过构建人工电子系统和研究自旋信息是如何交流的，该项目旨在了解在未来的技术中可以使用多长距离耦合的限制，在未来技术中，编程信息以电子自旋编码。从事这些项目的学生将学习技能，使他们能够成为学术或工业社区的富有成效的成员。*技术摘要*本项目将探索非局部自旋-自旋相互作用，类似于研究得很好的Ruderman-Kittel-Kasuya-Yosida(RKKY)相互作用，在基于栅定义的GaAs量子点的人工制造的自旋系统中，金属中局部自旋之间的相互作用。具体的实验将(1)研究RKKY和近藤效应之间的竞争，旨在揭示强关联电子材料中这种竞争的较不可控的竞争对手；(2)探索由弹道电子或小的受限费米海介导的RKKY相互作用；以及(3)通过弱局域测量观察自旋耦合对电子海本身的退相效应。该项目的第二个主要目标是探索使用自旋作为量子信息的持有者。由于RKKY相互作用非局域地传递自旋信息，因此在基于自旋的量子信息处理中，RKKY相互作用很有可能实现自旋信息的长程传输。然而，自旋与电子海的耦合可能会导致类似于Korringa弛豫的量子相干损失。该项目开发的实验技术将确定使用RKKY相互作用进行自旋信息的远程通信是否可能用于未来的技术。参与这项研究的学生将获得未来在学术界或工业或国家实验室工作所需的知识和技能。

*****NON-TECHNICAL ABSTRACT*****Spin, as the name suggests, is a fundamental property of electrons describing their angular momentum (as if they were spinning) and associated magnetic properties. While modern electronics predominantly use the charge of the electron to encode information, electron spin is also working for us, notably in hard drives, credit card strips, and any other magnetic storage medium. However, spin offers a much more powerful application-one that has yet to appear in any technology, but which theory has shown could lead to revolutionary improvements in computation and communication by tapping the laws of quantum mechanics. This project aims to study experimentally how information about spin orientation is conveyed between electrons in an intrinsically quantum mechanical way. Rather than investigating electrons in their natural environment, e.g., in a metal (which is difficult to probe and control), this project will fabricate artificial electronic systems from nanoscale semiconductors devices known as quantum dots, allowing far greater control over individual electrons. In quantum dots, spins can be coupled and uncoupled with the turn of a knob, as in a transistor. By constructing artificial electronic systems and investigating how spin information is communicated, the project aims to learn the limits of how long-range coupling can be used for future technologies in which programmed information is encoded in electron spin. The students working on these projects will learn skills that will enable them to become productive members of the academic or industrial communities.*****TECHNICAL ABSTRACT*****This project will explore non-local spin-spin interactions, analogs of the well-studied Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction between localized spins in metals, in an artificially fabricated spin system based on gate-defined GaAs quantum dots. Particular experiments will (1) investigate the competition between RKKY and Kondo effects, aiming to shed light on less controllable counterparts of this competition in strongly correlated electronic materials, (2) explore RKKY interactions mediated by ballistic electrons or a small confined fermi sea, and (3) to observe the dephasing effects of spin coupling on the electron sea itself through weak localization measurements. A second main goal of the project is to explore the use of spin as a holder of quantum information. Because the RKKY interaction conveys spin information nonlocally it is an interesting candidate to mediate the long-range transfer of spin information for spin-based quantum information processing. However, the coupling of spins to an electron sea presumably leads to losses of quantum coherence analogous to Korringa relaxation. Experimental techniques developed in this project will determine if long-range communication of spin information using RKKY interactions are possible for future technologies. The students involved with this research will obtain the knowledge and skills necessary for future careers in academe or in industrial or national laboratories.