Optical Studies of Spin in 2D Crystals

二维晶体中自旋的光学研究

• 批准号: 1310661
• 负责人: Roland Kawakami
• 金额: $ 40万
• 依托单位: Ohio State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-09-01 至 2016-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1310661&HistoricalAwards=false
• 关键词: Optical; Studies; Spin; 2D; Crystals

****Technical Abstract****Two-dimensional (2D) crystals are a fascinating new class of materials that exhibit novel electronic, spintronic, and optical properties. In this project, we will use optical techniques to investigate the spin-dependent properties of two types of 2D crystals: MoS2 (and related metal dichalcogenides) and graphene. Monolayer MoS2 is a direct gap semiconductor with a giant spin splitting of the valence band at the K/K' valleys. Interestingly, this is predicted to suppress most types of spin relaxation and generate long spin lifetimes for holes. Further, the giant spin splitting makes MoS2 a promising candidate for realizing the intrinsic spin Hall effect. Our aim is to observe these novel properties using time-resolved Kerr microscopy to directly measure the spin polarization and spin dynamics in MoS2. Graphene is a promising material for spintronics due to its long spin diffusion length at room temperature. The forefront of the field of graphene spintronics concerns the nature of spin relaxation and induced magnetism. Nearly all studies are based on spin transport, but this approach has its limitations such as spin relaxation induced by ferromagnetic contacts and reliance on Hanle analysis. We will utilize time-resolved optical techniques to overcome these limitations. Together, these studies on MoS2 and graphene lie at the forefront of spin-dependent physics in 2D crystals. This project will support the education of two PhD students, who will receive excellent training for careers in industry and academia.****Non-Technical Abstract****Two-dimensional (2D) crystals are a remarkable class of materials that exhibit fascinating new properties and have the potential to revolutionize electronics beyond conventional silicon technologies. In particular for spintronic devices, 2D crystals are exhibiting much better performance than their three-dimensional counterparts and special spin-dependent properties related to their 2D structure are predicted. Why does 2D perform better, can it be further improved, and can the predicted new properties be demonstrated? To answer such key questions, we will use powerful imaging techniques combining ultrafast pulsed lasers and optical microscopes to directly visualize the motion and rotation of electron spins in 2D crystals. The spin can be thought of as a tiny magnet that is attached to an electron as is flows through a device. In a spintronic device, the direction of an electron's magnetic poles ("north" and "south") is used to carry information throughout the device, and this information can be manipulated by rotating the direction of the poles. By using lasers and optics to image the motion and rotation of these magnetic poles (i.e. spin), we can investigate how they hold information, how they lose information, and how the direction of the poles is related to the electron's motion. Understanding these issues will enable the development of advanced spintronic devices for electronics beyond silicon. This project will support the education of two PhD students, who will receive excellent training for careers in industry and academia.

****技术摘要****二维（2D）晶体是一种引人入胜的新型材料，具有新颖的电子，自旋和光学特性。在这个项目中，我们将使用光学技术研究两种类型的2D晶体的自旋依赖性特性：MOS2（和相关的金属二核苷）和石墨烯。单层MOS2是一个直接的间隙半导体，在k/k'Valleys处的价带巨大的自旋分裂。有趣的是，预计这将抑制大多数类型的自旋松弛，并为孔产生长的自旋寿命。此外，巨型旋转分裂使MOS2成为实现固有的自旋效果的有前途的候选人。我们的目的是使用时间分辨的KERR显微镜观察这些新型特性，以直接测量MOS2中的自旋极化和自旋动力学。石墨烯是一种有前途的旋转基质材料，因为它在室温下的旋转扩散长度很长。石墨烯旋转型领域的最前沿涉及自旋松弛和诱导磁性的性质。 几乎所有研究都基于自旋运输，但是这种方法具有其局限性，例如铁磁接触引起的自旋松弛以及对汉尔分析的依赖。我们将利用时间分辨的光学技术来克服这些限制。共同，这些对MOS2和石墨烯的研究位于2D晶体中自旋依赖性物理的最前沿。该项目将支持两名博士学位学生的教育，他们将获得为行业和学术界的职业提供出色的培训。特别是对于自旋设备，2D晶体的性能比其三维对应物和与其2D结构相关的特殊自旋依赖性特性更好。为什么2D的性能更好，可以进一步改进，并且可以证明预测的新属性吗？为了回答这样的关键问题，我们将使用结合超快速脉冲激光器和光学显微镜的强大成像技术直接可视化2D晶体中电子旋转的运动和旋转。可以将自旋视为通过设备流的流量连接到电子上的微型磁铁。在自旋设备中，电子磁极（“北”和“南”）的方向用于整个设备中携带信息，并且可以通过旋转极点的方向来操纵此信息。通过使用激光器和光学元件来对这些磁极的运动和旋转（即自旋）成像，我们可以研究它们如何持有信息，如何丢失信息以及电线杆的方向与电子运动的方向如何。了解这些问题将使硅外电子设备的先进自旋设备的开发。该项目将支持两名博士学位学生的教育，他们将获得针对行业和学术界职业的出色培训。