Ultrafast study of spin-orbit materials by time and spin resolved photoemission spectroscopy

通过时间和自旋分辨光电子能谱对自旋轨道材料进行超快研究

• 批准号: 1410660
• 负责人: Alessandra Lanzara
• 金额: $ 32.45万
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Continuing 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=1410660&HistoricalAwards=false
• 关键词: Ultrafast; study; spin; orbit; materials

Non-technical abstract: The electron spin is a fascinating property of materials. Its binary nature "spin-up or -down" acts as the simplest example of quantization, and as such, it is often used as the starting point for quantum mechanics textbooks. The magnetic moment of the electron spin is a primary driver of the rich field of magnetism, and its interaction with the orbital motion (known as spin-orbit interaction), can have significant consequences such as the anomalous Hall effect in ferromagnets. Although present in some degree in all materials, only recently with the discovery of a new class of materials known as topological insulators (materials insulating on the bulk but metallic on the surface), it has been realized that spin-orbit coupling can be the driver of beautiful new phenomena in non-magnetic materials as well. This project focuses on an experimental investigation of the emergent spin dependent physics from spin-orbit coupling in a range of materials relevant to both fundamental materials science research and technology, with main focus on the three dimensional topological insulators. Students working on this project will develop expertise in material characterization methodologies and the evolving techniques of photoelectron spectroscopy to become future leaders of the new growing community of experimental spin-dynamics. This will prepare them for scientific careers in industry, academia or government laboratories. In conjunction with outreach programs at UC Berkeley, this project will involve minorities and young students to instill passion and curiosity for science.Technical abstract: A prominent topic in current condensed matter physics is the development of materials and devices that utilize the spin degree of freedom, in contrast to traditional electronics, which use only the electronic charge. The rapidly expanding field of spin-orbit coupled materials and the recent discovery of topological insulators constitute one exciting route to such control. Topological insulators are insulating materials characterized by a bulk bandgap, and massless Dirac fermion surface states which are spin non-degenerate and features unique spin-momentum locking in which states are strongly spin polarized along a spatial direction determined by the direction of their crystal momentum. This project seeks to advance our understanding of spin-orbit physics in three-dimensional topological insulators and on the interaction between topologically protected surface states and symmetry breaking materials, as well as to search for new way to manipulate the resulting spin texture with light. This is achieved by use of novel technique of time-, spin- and angle resolved photoemission spectroscopy. Students working on this project will develop expertise in the field of vacuum, material characterization, laser, optics and photoelectron spectroscopy. The project will also target minorities and young students through school-year mentorship and summer research projects.

非技术摘要：电子自旋是材料的一个迷人的属性。 它的二进制性质“自旋向上或向下”作为量子化的最简单的例子，因此，它经常被用作量子力学教科书的起点。电子自旋的磁矩是丰富磁场的主要驱动力，它与轨道运动的相互作用（称为自旋-轨道相互作用）可能会产生重大后果，例如铁磁体中的异常霍尔效应。 虽然在某种程度上存在于所有材料中，但直到最近才发现了一类称为拓扑绝缘体的新材料（体材料绝缘，但表面金属），人们已经意识到自旋轨道耦合也可以成为非磁性材料中美丽新现象的驱动因素。 该项目的重点是在一系列与基础材料科学研究和技术相关的材料中从自旋轨道耦合中涌现出的自旋相关物理的实验研究，主要关注三维拓扑绝缘体。 从事该项目的学生将发展材料表征方法和光电子能谱技术的专业知识，成为实验自旋动力学新增长社区的未来领导者。这将为他们在工业，学术界或政府实验室的科学生涯做好准备。该项目将与加州大学伯克利分校的外展计划相结合，让少数民族和年轻学生对科学充满热情和好奇心。技术摘要：当前凝聚态物理学的一个突出主题是开发利用自旋自由度的材料和器件，与传统的电子学相反，传统的电子学只使用电子电荷。 自旋-轨道耦合材料领域的迅速扩大和拓扑绝缘体的最新发现构成了这种控制的一条令人兴奋的途径。 拓扑绝缘体是以体带隙和无质量狄拉克费米子表面态为特征的绝缘材料，所述无质量狄拉克费米子表面态是自旋非简并的并且具有独特的自旋-动量锁定，其中状态沿着由其晶体动量的方向确定的空间方向被强烈自旋极化沿着。 该项目旨在推进我们对三维拓扑绝缘体中自旋轨道物理的理解，以及拓扑保护表面态与对称性破缺材料之间的相互作用，并寻找用光操纵所得自旋纹理的新方法。这是通过使用时间，自旋和角度分辨光电子能谱的新技术来实现的。从事该项目的学生将发展真空，材料表征，激光，光学和光电子能谱领域的专业知识。该项目还将通过学年指导和暑期研究项目，以少数民族和青年学生为对象。