EFRI 2-DARE Proposal: Spin-Valley Coupling for Photonic and Spintronic Devices

EFRI 2-DARE 提案：光子和自旋电子器件的自旋谷耦合

• 批准号: 1433496
• 负责人: David Cobden
• 金额: $ 150万
• 依托单位: University of Washington
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-08-15 至 2018-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1433496&HistoricalAwards=false
• 关键词: EFRI; DARE; Proposal; Spin; Valley

Non-Technical: The performance and capabilities of key present solid-state technologies, such as light-emitting diodes, solar cells, and other electro-optic components, are ultimately constrained by the fundamental properties of conventional semiconductors such as silicon and gallium arsenide. Monolayers of the layered transition-metal dichalcogenides (with formula MX2, such as MoS2 and WSe2) have recently been discovered to be a new class of semiconductors effectively at the atomically thin limit. They have dramatically different fundamental properties which can defy previous constraints, allowing observation and discovery of new physical phenomena and offering potential for unprecendented solid-state device possibilities. Fundamentally new properties in MX2 include the relationship between electron spin, the "valley index" specifying which of two equivalent momentum states the electron occupies in the 2D lattice, and the "layer index" specifying which layer the electron is in when two monolayers form a bilayer. The spin, valley and layer quantum numbers in this material are linked and can be manipulated jointly, as has already been demonstrated theoretically and experimentally by the investigators. The proposed work aims to study all aspects of this "spin-valley-layer coupling", ranging from its role in electrical transport to its interplay with optical cavities, with a view to novel yet practical device technologies with electrical, magnetic, and optical control. The work will be done by a mixed team of physics and engineers and will provide interdisciplinary research education to a large number of graduate and undergraduate students.Technical: In monolayer MX2 the strong spin-orbit coupling locks the real spin at the band edges to the valley index to produce spin-valley coupling. At the same time the valleys, and hence spins, are addressable using circularly polarized optical selection rules. Additionally, in bilayers and heterostructures the valley index is further coupled to the layer index for a given valley index, leading to new magnetoelectric effects. MX2s thus provide the first solid-state system in which electric and dynamical control of combined valley pseudospin and real spin are possible, opening up a wealth of hybrid spin and valley device possibilities. The focus of the proposed work is on the studying the unique spin, valley and layer pseudospin couplings in MX2 monolayers, bilayers and heterostructures with photonic and spintronic device applications in mind. The specific goals and methods are as follows: (1) develop microscopic theories for coupled spin-valley-charge transport to guide and model the experimental efforts and synthesis of monolayers, bilayers, heterostructures, and hybrid systems; (2) develop highest quality, large-area crystal growth with controllable charged and magnetic dopants; (3) combine electrical and optical investigation of intrinsic spin and valley properties to determine the fundamental parameters of monolayers and bilayers in various device geometries for hybrid spin-valleytronics; (4) investigate and demonstrate manipulation of spin and valley polarizations in heterostructures and hybrid photonic devices combining MX2s with structures such as photonic-crystal cavities, addressing aspects including spin-valley-charge transport across interfaces, interlayer exciton physics, exciton-polaritons in integrated cavity structures, and strong photon-valley exciton interactions within a nanocavity; and (5) develop MX2 lateral junction devices for efficient, controllable, and spin and valley specific light emitters, modulators and detectors.

非技术性：关键目前的固态技术的性能和能力，例如发光二极管，太阳能电池和其他电磁组件，最终受到常规半导体（例如硅和甘油衣）的基本特性的限制。最近已经发现，分层过渡金属二分法（具有MOS2和WSE2等公式MX2）的单层是在原子上薄的极限下有效地是一种有效的新半导体。它们具有截然不同的基本属性，可以无视以前的约束，从而可以观察和发现新的物理现象，并为前所未有的固态设备可能性提供了潜力。 MX2中的根本新特性包括电子旋转之间的关系，“山谷索引”指定了两个等效动量中的哪个表示电子在2D晶格中占据，而“层索引”指定了两个单层形成双层时电子的层。该材料中的自旋，山谷和层量子数是连接的，可以共同操纵，研究人员在理论上和实验上已经证明了这一点。提出的工作旨在研究这种“自旋 - 瓦利层耦合”的各个方面，从其在电气传输中的作用到与光腔的相互作用，都可以看到具有电气，磁性和光学控制的新颖但实用的设备技术。这项工作将由一组混合的物理和工程师团队完成，并将向大量的研究生和本科生提供跨学科的研究教育。技术：在单层MX2中，强的旋转轨道耦合锁定了真正的旋转，将真正的旋转锁定到山谷索引，以产生Spin-Valley耦合。同时，使用圆形极化的光学选择规则可以解决山谷，因此可以旋转。此外，在双层和异质结构中，山谷指数进一步耦合到给定山谷指数的层指数，从而导致新的磁电效应。因此，MX2提供了第一个固态系统，在该系统中，可以对山谷伪旋转和真实旋转进行电和动态控制，从而打开了大量混合自旋和山谷设备的可能性。拟议的工作的重点是研究在MX2单层，双层和异质结构中使用光子和自旋设备应用的独特旋转，山谷和伪旋转耦合。具体目标和方法如下：（1）开发用于耦合自旋 - 瓦利 - 充电运输的微观理论，以指导和建模单层，双层，异质结构和混合系统的实验工作和合成； （2）发展具有可控和磁性掺杂剂的最高质量，大面积晶体生长； （3）结合了内在自旋和山谷特性的电气和光学研究，以确定用于混合自旋valleytronics的各种设备几何形状中单层和双层的基本参数； (4) investigate and demonstrate manipulation of spin and valley polarizations in heterostructures and hybrid photonic devices combining MX2s with structures such as photonic-crystal cavities, addressing aspects including spin-valley-charge transport across interfaces, interlayer exciton physics, exciton-polaritons in integrated cavity structures, and strong photon-valley exciton interactions within a nanocavity; （5）开发MX2侧连接设备，以进行有效，可控制和旋转和山谷的特定光发射器，调节器和检测器。