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) 晶体是一类令人着迷的新型材料，具有新颖的电子、自旋电子和光学特性。在这个项目中，我们将使用光学技术来研究两种类型的二维晶体的自旋相关特性：MoS2（和相关的金属二硫化物）和石墨烯。单层MoS2是一种直接带隙半导体，在K/K'谷处具有巨大的价带自旋分裂。有趣的是，预计这将抑制大多数类型的自旋弛豫并为空穴产生较长的自旋寿命。此外，巨大的自旋分裂使得MoS2成为实现本征自旋霍尔效应的有希望的候选者。我们的目标是使用时间分辨克尔显微镜来观察这些新特性，以直接测量 MoS2 中的自旋极化和自旋动力学。石墨烯由于在室温下具有较长的自旋扩散长度，是一种有前途的自旋电子学材料。石墨烯自旋电子学领域的前沿涉及自旋弛豫和感应磁性的本质。 几乎所有的研究都是基于自旋输运，但这种方法有其局限性，例如铁磁接触引起的自旋弛豫以及对汉勒分析的依赖。我们将利用时间分辨光学技术来克服这些限制。总之，这些关于 MoS2 和石墨烯的研究处于二维晶体中自旋相关物理学的前沿。该项目将支持两名博士生的教育，他们将接受工业界和学术界职业生涯的优秀培训。****非技术摘要****二维 (2D) 晶体是一类非凡的材料，它表现出令人着迷的新特性，并有潜力超越传统硅技术，彻底改变电子学。特别是对于自旋电子器件，二维晶体表现出比三维晶体更好的性能，并且预测了与其二维结构相关的特殊自旋相关特性。为什么 2D 表现更好，是否可以进一步改进，是否可以证明预测的新特性？为了回答这些关键问题，我们将使用强大的成像技术，结合超快脉冲激光和光学显微镜，直接可视化二维晶体中电子自旋的运动和旋转。自旋可以被认为是一个微小的磁铁，当电子流经设备时，它会附着在电子上。在自旋电子器件中，电子磁极的方向（“北”和“南”）用于在整个器件中携带信息，并且可以通过旋转磁极的方向来操纵该信息。通过使用激光和光学对这些磁极的运动和旋转（即自旋）进行成像，我们可以研究它们如何保存信息、如何丢失信息以及磁极的方向与电子运动的关系。了解这些问题将有助于开发硅以外的先进电子自旋电子器件。该项目将支持两名博士生的教育，他们将接受工业界和学术界职业生涯的良好培训。