Electron and Nuclear Spin Interactions in Low-Dimensional Semiconductors

非技术电子是具有自旋、质量和电荷的基本粒子。对电子能级的理解对于理解化学和半导体等固态材料的发展至关重要，固态材料使计算机芯片、发光二极管和太阳能电池等技术成为可能。当今计算机芯片中的逻辑元件依赖于控制电子电荷，并根据电荷电流和电压的存在与否对信息进行编码，但使用电子自旋极化来编码信息在量子信息处理方面具有应用价值，并在提高逻辑器件的速度、效率和能耗方面具有潜在优势。然而，电子自旋也与核自旋相互作用，这可能是一个不受欢迎的噪音来源，或者，如果我们能更好地理解它，这是控制电子自旋极化的途径。PI将使用脉冲激光的光学测量来表征这些自旋相互作用如何依赖于材料应变和其他参数。这项研究将提高对这些相互作用的科学理解，并帮助我们找到控制它们的方法。这项研究的结果有可能推动包括半导体物理、设备工程、材料科学、磁学和量子信息在内的多个科学和技术领域的发展。这项研究将为学生研究人员提供各种技术方面的宝贵培训，包括半导体器件设计和制造、光学和电学测量、数据采集和分析以及通过科学报告和出版物交流结果。拟议的外联和教育活动将寻求增加公众对科学和技术最新发展的参与，并鼓励代表性不足的群体参与科学事业。技术研究拟议的研究将研究低维半导体异质结中的电子和核自旋相互作用。控制电子和核自旋之间的相互作用对于经典和量子信息处理等应用具有重要意义，但对电子-核自旋耦合系统的认识还不完全。最近对应变量子点的实验揭示了一些意想不到的现象，包括核自旋锁定、零磁场核磁化和反常Hanle效应。这些现象被不同程度地归因于量子限制效应、介观尺寸效应和应变效应，但很难在量子点中分离这些效应并建立其潜在的物理机制。对应变和非应变量子阱的测量将阐明量子限制、载流子局域化、约化对称性和维度以及自旋-轨道效应对电子-核自旋相互作用的影响。将使用超快泵浦探测和自旋噪声光学技术监测核极化，这些技术能够灵敏地测量核自旋极化的微小变化。这项拟议的研究将促进对最近在应变量子点中观察到的现象的物理起源的科学理解，并解决关于电子-核自旋耦合系统及其与光的相互作用的公开问题。

Non-TechnicalElectrons are fundamental particles that have spin, mass, and charge. The understanding of electronic energy levels has been crucial to understanding chemistry and the development of solid-state materials, such as semiconductors, which have enabled technologies such as computer chips, light-emitting diodes, and solar cells. The logic elements in today's computer chips rely on controlling electron charge and encode information as the presence or absence of charge currents and voltages, but encoding information using electron spin polarization has applications for quantum information processing and potential advantages for improving the speed, efficiency, and energy consumption of logic devices. Electron spins, however, also interact with nuclear spins, and this can be an undesirable source of noise or, if we can understand it better, a pathway for controlling electron spin polarization. The PI will use optical measurements with pulsed lasers to characterize how these spin interactions depend on material strain and other parameters. This research will improve the scientific understanding of these interactions and help us figure out how to control them. The results of this research have the potential to advance multiple scientific and technological areas, including semiconductor physics, device engineering, materials science, magnetism and quantum information. The research will provide valuable training to student researchers in a wide range of techniques, including semiconductor device design and fabrication, optical and electrical measurements, data acquisition and analysis and communicating results through scientific presentations and publications. The proposed outreach and education activities will seek to increase public engagement with recent developments in science and technology and to encourage the participation of underrepresented groups in scientific careers.TechnicalThe proposed research will investigate electron and nuclear spin interactions in low-dimensional semiconductor heterostructures. Controlling the interactions between electron and nuclear spins is of great importance for applications such as classical and quantum information processing, but the understanding of the coupled electron-nuclear spin system is incomplete. Recent experiments on strained quantum dots have revealed unexpected phenomena, including nuclear spin locking, nuclear magnetization at zero magnetic field, and the anomalous Hanle effect. These phenomena have been variously attributed to the effects of quantum confinement, mesoscopic size, and strain, but it is difficult to separate these effects in quantum dots and establish the underlying physical mechanisms. The proposed measurements on strained and unstrained quantum wells will elucidate the role of quantum confinement, carrier localization, reduced symmetry and dimensionality, and spin-orbit effects on electron-nuclear spin interactions. The nuclear polarization will be monitored using ultrafast pump-probe and spin noise optical techniques capable of sensitively measuring small changes to the nuclear spin polarization. The proposed research will advance scientific understanding of the physical origins of recently-observed phenomena in strained quantum dots and address open questions about the coupled electron-nuclear spin system and its interaction with light.