Spin Dependent Transport in Materials with Multivalley Band Structures

多谷带结构材料中的自旋相关输运

• 批准号: 1503601
• 负责人: Hanan Dery
• 金额: $ 29.43万
• 依托单位: University of Rochester
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-01 至 2019-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1503601&HistoricalAwards=false
• 关键词: Spin; Dependent; Transport; Materials; Multivalley

NONTECHNICAL SUMMARYThis award supports fundamental theoretical research and education to understand how electron spin behaves in materials contributing to the foundations of possible future electronic devices which function by manipulating electron spin as well as its charge. In addition to carrying an electric charge, an electron is also in a sense like a spinning top that behaves according to the rules of quantum mechanics. There are two senses of spin to an electron and it is natural to explore using the electron to physically represent information, like the familiar '0' and '1' in digital electronics. Spintronics research aims to introduce the quantum mechanical spin into electronic devices by making use of the interactions between the electron spin and its environment in a material. Because charge-based field effect transistors are rapidly approaching their physical limits, the spin-charge computation scheme has recently become an active research frontier.The PI will develop theoretical models that quantify spin transport in materials that include silicon and elements vertically above and below silicon in the periodic table of elements. The PI will also investigate crystals that are essentially a single layer of atoms such as transition-metal dichalcogenides which are made of atoms from the transition-metal block of the periodic table and elements from the periodic table vertically below oxygen. This modeling is aimed to enable the design of spintronic devices in which the time needed for manipulating and processing information is prolonged by strain engineering and proper application of external electric fields. The primary research focus will be on quantifying this spin relaxation time in doped materials where the conductivity is improved either by intentionally adding foreign atoms that donate/accept electrons to/from the host crystal, or by applying a gate-voltage that brings charge carriers into atomically thin materials from surrounding materials. This project presents ideas that are fascinating to a wide range of students. Through collaboration of materials science, physics and engineering graduate students, each learns from the other concepts of quantum mechanics or device function. The PI will actively promote this research among K-12 students by delivering interactive lectures/demos that highlight the use of future technology in devices. The PI aims to utilize the potential of this research for societal impact to help attract students from under-represented groups to the project.TECHNICAL SUMMARYUnderstanding of the interactions between the electron's spin and its solid-state environment in metallic material systems has spurred immense development in information storage technologies. Contrary to metals, silicon holds complete sway over logic circuits. Fortunately, this and other group IV materials are promising candidates for spintronic logic devices owing to their crystalline inversion symmetry which suppresses precession of spins about randomly changing intrinsic magnetic fields, and the zero nuclear spin of their naturally abundant isotopes which suppresses spin relaxation by hyperfine interactions. A major objective in this project will be to fill a longstanding gap in the theory of spin relaxation processes in multi-valley semiconductors such as silicon and germanium. The spin relaxation in these materials shows a strong dependence on the identity of the donor atom. By invoking analytical and numerical methods, the PI will quantify the donor-driven spin relaxation by establishing a connection with the induced changes in the donor ground state due to the spin orbit coupling. The effect will be investigated as a function of strain, temperature, donor concentration, and donor identity. Apart from group IV materials, monolayer transition-metal dichalcogenides and oxides present another important class of materials potentially useful for spintronics. These two-dimensional monolayer semiconductors put together exotic charge, spin and valley electronic phenomena. The strong binding between electrons and holes, a result of the impeded Coulomb screening in genuine 2D systems, enables exceptionally strong light-matter interaction that persists up to room temperature.The PI will systematically quantify the momentum scattering and spin relaxation due to electron-phonon interaction in two-dimensional crystals such as graphene and transition-metal dichalcogenides. Transport effects will include signatures of electrical fields via piezoelectricity and symmetry breaking by the gate voltage. The PI will also analyze the often-discussed topological insulator phase in two-dimensional crystals from the perspective of relaxation.The PI aims to recruit qualified undergraduate students to participate in the research, and teach a new course on spintronics which explains how quantum mechanics and magnetism can be applied into new logic and memory architectures. The PI will try to recruit McNair scholars and will work with the Kearns Center at the University of Rochester to attract students from under-represented minorities to this research.

非技术总结该奖项支持基础理论研究和教育，以了解电子自旋在材料中的行为，为未来可能的电子设备奠定基础，这些设备通过操纵电子自旋及其电荷来发挥作用。除了携带电荷，电子在某种意义上也像一个旋转的陀螺，它的行为符合量子力学的规则。电子的自旋有两种感觉，探索使用电子来物理表示信息是很自然的，就像数字电子中熟悉的‘0’和‘1’一样。自旋电子学研究旨在通过利用材料中电子自旋与其环境之间的相互作用，将量子力学自旋引入电子器件。由于基于电荷的场效应晶体管正在迅速接近其物理极限，自旋电荷计算方案最近已成为一个活跃的研究前沿。PI将开发理论模型来量化材料中的自旋输运，这些材料包括硅以及元素周期表中垂直于硅上下的元素。PI还将研究本质上是单层原子的晶体，如过渡金属二卤化物，它由元素周期表中过渡金属块的原子和元素组成，垂直低于氧气。这种建模的目的是使自旋电子器件的设计能够通过应变工程和适当地施加外部电场来延长处理和处理信息所需的时间。主要的研究重点将是量化掺杂材料中的自旋弛豫时间，在掺杂材料中，通过故意添加向宿主晶体提供电子/从宿主晶体接受电子的外来原子，或者通过施加栅极电压将电荷载流子从周围材料带入原子薄的材料中，来改善导电性。这个项目提出的想法，吸引了广泛的学生。通过材料科学、物理和工程学研究生的合作，每个人都可以学习量子力学或设备函数的其他概念。PI将通过提供互动讲座/演示，强调未来技术在设备中的使用，在K-12学生中积极促进这项研究。PI旨在利用这项研究的社会影响潜力来帮助吸引来自代表性不足群体的学生参与该项目。技术综述了解金属材料系统中电子自旋与其固态环境之间的相互作用已推动信息存储技术的巨大发展。与金属相反，硅对逻辑电路具有完全的影响力。幸运的是，这种材料和其他IV族材料很有希望成为自旋电子逻辑器件的候选者，因为它们的晶体反转对称性抑制了自旋关于随机变化的内禀磁场的进动，并且它们丰富的自然同位素的零核自旋抑制了超精细相互作用引起的自旋弛豫。该项目的一个主要目标将是填补多谷半导体(如硅和锗)中自旋弛豫过程理论的长期空白。这些材料中的自旋弛豫对施主原子的同一性有很强的依赖性。通过引用解析和数值方法，PI将通过建立与自旋轨道耦合引起的施主基态变化的联系来量化施主驱动的自旋弛豫。这种影响将作为菌株、温度、供体浓度和供体身份的函数进行调查。除了第四族材料外，单层过渡金属二卤化物和氧化物是另一类可能用于自旋电子学的重要材料。这些二维单层半导体将奇异的电荷、自旋和山谷电子现象结合在一起。在真正的2D系统中，由于受阻的库仑屏蔽，电子和空穴之间的强结合使极强的光-物质相互作用能够持续到室温。PI将系统地量化石墨烯和过渡金属二卤化物等二维晶体中由于电子-声子相互作用而产生的动量散射和自旋弛豫。输运效应将包括通过压电性的电场签名和栅极电压的对称性破坏。PI还将从松弛的角度分析经常讨论的二维晶体中的拓扑绝缘体相。PI的目标是招募合格的本科生参与这项研究，并教授一门新的自旋电子学课程，解释如何将量子力学和磁学应用于新的逻辑和存储架构。国际学生联合会将努力招募麦克奈尔学者，并将与罗切斯特大学的卡恩斯中心合作，吸引来自代表性不足的少数族裔的学生参加这项研究。