Spin Transport Far From Equilibrium

技术摘要：本项目将促进对半导体在远离平衡状态下的电荷和自旋输运的理解。该研究解决了使用铁磁性金属产生和检测半导体自旋电流的新设备。实验将探讨自旋轨道相互作用、超精细相互作用、热电子居群和维度如何影响自旋极化输运等基本现象。首先，将进行一系列实验，以阐明半导体中的自旋霍尔效应（最近才在输运测量中观察到）与其反向效应（自旋极化电流产生电荷电流）之间的联系。第二组实验将探测远离平衡态的自旋极化载流子，最近已经观察到这些载流子偏离了普通的线性响应。利用这些非线性效应来控制自旋电流的潜力将被证明。第三，传统输运效应中自旋-轨道耦合的表现，包括弱反局域化，将与使用PI团队开发的技术对自旋输运和动力学的直接测量相关联。最后，提出的研究将解决一些关键步骤，需要进行类似的实验在减少的维度。这些实验解决了实现器件（如自旋晶体管）所需的一些关键步骤，这将需要对铁磁-半导体异质结构有更深入的了解。磁性在现代技术中无处不在。像计算机硬盘驱动器那样的海量数据存储依赖于铁、钴或镍等金属的磁性。半导体虽然也是现代技术的重要组成部分，但它没有磁性。这个项目的重点是由铁磁性材料（铁）和半导体的薄层组成的材料系统。这条研究路线的最终目标是实现在单个芯片上进行信息处理和存储的新型设备。这个项目的重点是决定如何在半导体中注入、控制和检测电子自旋（磁性信息的载体）的基本特性。这项研究将包括实验，探索在半导体表面附近、大量或非常薄的层中产生自旋时出现的新的和不寻常的情况。这些物理现象是本研究可能实现的磁电子器件新提案的核心。

Technical abstractThis project will advance the understanding of charge and spin transport in semiconductors under conditions that are very far from equilibrium. The research addresses new devices in which spin currents in semiconductors are generated and detected using ferromagnetic metals. The experiments will address how fundamental phenomena such as the spin-orbit interaction, hyperfine interactions, hot electron populations, and dimensionality impact spin-polarized transport. First, a set of experiments will be carried out to elucidate the connection between the spin Hall effect in semiconductors, which has only recently been observed in transport measurements, and its inverse effect, in which a spin-polarized current generates a charge current. A second set of experiments will probe spin-polarized carriers far from equilibrium, where departures from ordinary linear response have recently been observed. The potential for using these non-linear effects to control spin currents will be demonstrated. Third, the manifestation of spin-orbit coupling in traditional transport effects, including weak-anti-localization, will be correlated with direct measurements of the spin transport and dynamics using techniques developed in the PI's group. Finally, the proposed research will address some of the critical steps required to undertake similar experiments in reduced dimensions. These experiments address some of the critical steps required to implement devices, such as a spin transistor, which will require a deeper understanding of ferromagnet-semiconductor heterostructures.Non-technical abstract Magnetism is ubiquitous in modern technology. Mass data storage, as in computer hard drives, depends on the magnetism of metals, such as iron, cobalt or nickel. Semiconductors, while also a critical component of modern technologies, are not magnetic. This project focuses on a materials system that is made out of thin layers of a ferromagnetic material (iron) and a semiconductor. The ultimate goal of this line of research is the achievement of new classes of devices that carry out both the processing and storage of information on a single chip. This project focuses on fundamental properties that determine how electron spins (the carriers of magnetic information) can be injected, controlled, and detected inside a semiconductor. The research will include experiments probing the new and unusual conditions present when spins in semiconductors are generated near surfaces, in very large numbers, or in very thin layers. These physical phenomena lie at the heart of new proposals for magneto-electronic devices that could be enabled by this research.