Coupled Charge and Spin Transport in Topological Insulators

拓扑绝缘体中的耦合电荷和自旋输运

• 批准号: 1128304
• 负责人: Roger Lake
• 金额: $ 36万
• 依托单位: University of California-Riverside
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-09-01 至 2014-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1128304&HistoricalAwards=false
• 关键词: Coupled; Charge; Spin; Transport; Topological

Topological insulators constitute a new class of quantum materials with bulk insulating energy gaps and gapless Dirac-cone edge or surface states. The surface states are protected against time-reversal-invariant perturbations such as non-magnetic impurities, defects, and reconstruction. The charge is uniquely coupled to the spin, and charge current creates spin polarization. Since the surface states are topologically protected, and the momentum states are coupled to spin states, scattering is reduced and noise is suppressed. In thin topological insulators, a Rashba-type spin splitting occurs which can be controlled by a gate voltage. The thermoelectric figure of merit, ZT, increases as film thickness is reduced. In summary, topological insulators have shown exceptional properties for thermoelectric, charge, and spin transport. These materials and properties will be investigated from an engineering electronics point of view. Devices that exploit these properties will be built, modeled and characterized, and the performance metrics and fundamental limits of such devices will be determined. Intellectual Merit: This investigation will be simultaneously carried out both experimentally and theoretically. The project will (i) add to the fundamental knowledge of the material properties and physical processes in highly-scaled topological insulator materials; (ii) build, model, and characterize devices that exploit topological insulating properties for computation, signal processing, and sensing; (iii) determine the performance metrics and the fundamental limitations of such devices, (iv) explore the use of topological insulators for low-dissipation, low-noise interconnects; and (v) develop the electrochemical atomic layer deposition technique to grow few-atomic-layer films of topological insulators. All materials will be extensively characterized using a wide range of methods including atomic force, scanning electron, and transmission electron microscopy, low energy electron diffraction, X-ray spectroscopy, Auger spectroscopy, electron probe micro-analysis, micro-Raman spectroscopy, electrical, and thermal measurements. Experimental measurements will be compared to device models and ab initio, density functional theory calculations of the electronic structure and vibrational modes of the thin film and nanowire materials. Transformative concepts include the use of low-dissipation, low noise topologically protected states of topological insulators for electronic / spintronic devices and low-noise, low-power interconnects.Broader Impact: The successful project has the potential to lead to new technologies that exploit the low-dissipation, low-noise states of topological insulators for computation, communications, and sensors. The broader impacts of this project affect all 5 example areas described within the grant proposal guide, and they are particularly strong in the areas of (i) broadening participation of underrepresented groups and (ii) promoting teaching and training through undergraduate research. The University of California Riverside is a Hispanic serving institution with the largest Hispanic student population among all of the University of California campuses. The principal investigator and co-principal investigator have a long history of successful supervision of underrepresented minorities, they served as principal investigator and co-principal investigator of the National Science Foundation Research Experience for Undergraduates Site for Nano Materials and Devices that focused on minority undergraduate student participation in research, and they plan to hire minority graduate and undergraduate students as research assistants for this project.

拓扑绝缘体是一类具有体绝缘能隙和无隙的Dirac锥边缘态或表面态的新型量子材料。保护表面状态免受时间反演不变的扰动，如非磁性杂质，缺陷和重建。电荷唯一地耦合到自旋，并且电荷电流产生自旋极化。由于表面态被拓扑保护，动量态与自旋态耦合，散射减少，噪声被抑制。在薄的拓扑绝缘体中，发生Rashba型自旋分裂，其可以由栅极电压控制。热电优值ZT随着膜厚度的减小而增大。总之，拓扑绝缘体在热电、电荷和自旋输运方面表现出了特殊的性质。这些材料和性能将从工程电子学的角度进行研究。利用这些属性的设备将被构建，建模和表征，并确定这些设备的性能指标和基本限制。智力优势：这项研究将同时进行实验和理论。该项目将（i）增加对高尺度拓扑绝缘体材料的材料特性和物理过程的基础知识;（ii）构建、建模和表征利用拓扑绝缘特性进行计算、信号处理和传感的设备;（iii）确定这种器件的性能指标和基本限制，（iv）探索拓扑绝缘体用于低耗散的用途，低噪声互连;以及（v）发展电化学原子层沉积技术以生长拓扑绝缘体的少原子层膜。所有材料都将使用广泛的方法进行广泛的表征，包括原子力，扫描电子和透射电子显微镜，低能电子衍射，X射线光谱，俄歇光谱，电子探针显微分析，显微拉曼光谱，电学和热学测量。实验测量将比较设备模型和从头算，密度泛函理论计算的电子结构和振动模式的薄膜和纳米线材料。变革性的概念包括将低耗散、低噪声拓扑保护态的拓扑绝缘体用于电子/自旋电子器件和低噪声、低功耗互连。更广泛的影响：该成功项目有可能导致新技术的开发，利用低耗散、低噪声态的拓扑绝缘体用于计算、通信和传感器。该项目的广泛影响影响到赠款提案指南中描述的所有5个示例领域，并且在以下领域特别强大：（i）扩大代表性不足的群体的参与;（ii）通过本科研究促进教学和培训。加州滨江大学是一所西班牙裔服务机构，拥有加州大学所有校区中最大的西班牙裔学生人口。首席研究员和联合首席研究员有着成功监督代表性不足的少数民族的悠久历史，他们曾担任国家科学基金会纳米材料和设备本科生研究经验网站的首席研究员和联合首席研究员，该网站专注于少数民族本科生参与研究，并计划聘请少数民族研究生和本科生作为研究助理。