Quantum Spin-Orbital Systems: Models and Spectroscopies

量子自旋轨道系统：模型和光谱

• 批准号: 1005932
• 负责人: Natalia Perkins
• 金额: $ 24.9万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-09-15 至 2014-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1005932&HistoricalAwards=false
• 关键词: Quantum; Spin; Orbital; Systems; Models

TECHNICAL SUMMARY This award supports theoretical and computational research and educational activities aimed at advancing our understanding of quantum systems, in which spin and orbital degrees of freedom are strongly coupled. Relevant materials are transition metal oxides on frustrated lattices. The research has two parts. The first part is devoted to the study of the fundamental properties of strongly interacting electron systems with coupled spin and orbital fluctuations. Vanadates are perhaps the most prominent examples of spin-orbital systems. The research in this part is motivated by recent experiments on several vanadates including spinel ZnV2O4 and quasi one-dimensional CaV2O4, in which reduced dimensionality appears because of a particular structure of orbital interactions. The PI will study relevant one-dimensional spin-orbital systems. The vanadium chains in these compounds are characterized by frustrated magnetic interactions, Ising-like orbital exchanges, and a large relativistic spin-orbit interaction. Corresponding one-dimensional spin-orbital systems are in many aspects different from the famous one-dimensional SU(4) model. The PI intends to investigate these models using both analytical and numerical theoretical techniques, including bosonization and density matrix renormalization group. The second part of the proposal is devoted to the development of the theory of two-magnon and two-orbiton Raman scattering in coupled spin-orbital systems. This is a challenging but rewarding project as the theory can be readily applied to understanding a variety of existing experimental data in correlated materials with coupled spin and orbital degrees of freedom. Special emphasis will be given to the study of Raman scattering from antiferromagnets, orbitally ordered states, and spin-orbital liquids on frustrated lattices. The PI will be engaged in educational activities at the graduate level aimed at refining and enhancing courses in solid state, statistical and many-body physics. She will develop an advanced course in strongly correlated phenomena in complex systems with special emphasis on new trends in magnetism and transport phenomena. A graduate student will be involved in the research activity. The PI will organize, in collaboration with other faculty from UW-Madison, a Wisconsin Winter School on Modern Condensed Matter and Quantum Information, which will introduce young researchers to various problems in the field and will also improve collaboration between faculty, students, and postdocs from all campuses of the University of Wisconsin system. NONTECHNICAL SUMMARY This award supports theoretical and computational research and educational activities aimed at advancing our understanding of materials, in which the electron spin, an intrinsic quantum mechanical property of electrons, and the motion of the electron strongly interact with each other. The relevant materials are oxides that include transition metals, for example vanadium or zinc, with certain spatial arrangements of atoms leading to spin or spatial distribution of electrons which can occur in many nearly equivalent and hence, competing ways. Achieving a theoretical understanding of the properties of these strongly correlated materials is challenging. Interest in these systems stems in part from the richness of their novel properties: the unexpected variety of ordered states, like various forms of magnetism, the transformations among them, and their sensitivity to stresses, such as applied electric or magnetic fields. The PI will use state-of-the-art analytical as well as computational tools to investigate the physical properties of such transition metal oxides, predict new effects in these materials, and contribute to understanding of experiments. The PI will be engaged in educational activities at the graduate level aimed at refining and enhancing courses in solid state, statistical and many-body physics. She will develop an advanced course in strongly correlated phenomena in complex systems with special emphasis on new trends in magnetism and electron transport phenomena. A graduate student will be involved in the research activity. The PI will organize, in collaboration with other faculty from UW-Madison, a Wisconsin Winter School on Modern Condensed Matter and Quantum Information, which will introduce young researchers to various problems in the field and will also improve collaboration between faculty, students, and postdocs from all campuses of the University of Wisconsin system.

该奖项支持理论和计算研究以及教育活动，旨在促进我们对量子系统的理解，其中自旋和轨道自由度强烈耦合。相关材料是阻挫晶格上的过渡金属氧化物。本研究分为两部分。第一部分是研究具有自旋和轨道耦合涨落的强相互作用电子系统的基本性质。钒酸盐也许是自旋轨道系统最突出的例子。这一部分的研究是由最近几个钒酸盐的实验，包括尖晶石ZnV_2O_4和准一维CaV_2O_4，其中降维出现，因为一个特殊的结构的轨道相互作用。PI将研究相关的一维自旋轨道系统。这些化合物中的钒链的特征在于受抑的磁相互作用，Ising类轨道交换，以及大的相对论自旋轨道相互作用。相应的一维自旋轨道系统在许多方面不同于著名的一维SU（4）模型。PI打算使用分析和数值理论技术来研究这些模型，包括玻色化和密度矩阵重整化群。第二部分的建议是致力于发展理论的两个磁振子和两个轨道的拉曼散射耦合自旋轨道系统。这是一个具有挑战性但有价值的项目，因为该理论可以很容易地应用于理解具有耦合自旋和轨道自由度的相关材料中的各种现有实验数据。特别强调反铁磁体、轨道有序态和自旋轨道液体在阻挫晶格上的拉曼散射的研究。PI将从事研究生水平的教育活动，旨在完善和加强固态，统计和多体物理学课程。她将开发一个先进的课程在复杂系统中的强相关现象，特别强调在磁性和运输现象的新趋势。一名研究生将参与这项研究活动。PI将与威斯康星大学麦迪逊分校的其他教师合作，组织一个关于现代凝聚态物质和量子信息的威斯康星州冬季学校，该学校将向年轻研究人员介绍该领域的各种问题，并将改善教师，学生和博士后之间的合作威斯康星州大学系统的所有校区。非技术总结该奖项支持理论和计算研究以及教育活动，旨在促进我们对材料的理解，其中电子自旋（电子的固有量子力学性质）和电子的运动相互强烈相互作用。相关材料是包括过渡金属（例如钒或锌）的氧化物，其具有导致电子的自旋或空间分布的原子的某些空间排列，所述自旋或空间分布可以以许多几乎等同的方式发生，并且因此以竞争的方式发生。实现对这些强相关材料的性质的理论理解是具有挑战性的。对这些系统的兴趣部分源于其新颖性质的丰富性：意想不到的各种有序状态，例如各种形式的磁性、它们之间的转变以及它们对应力（例如施加的电场或磁场）的敏感性。PI将使用最先进的分析和计算工具来研究这些过渡金属氧化物的物理特性，预测这些材料中的新效应，并有助于理解实验。PI将从事研究生水平的教育活动，旨在完善和加强固态，统计和多体物理学课程。她将开发一个先进的课程在复杂系统中的强相关现象，特别强调在磁性和电子传输现象的新趋势。一名研究生将参与这项研究活动。PI将与威斯康星大学麦迪逊分校的其他教师合作，组织一个关于现代凝聚态物质和量子信息的威斯康星州冬季学校，该学校将向年轻研究人员介绍该领域的各种问题，并将改善教师，学生和博士后之间的合作威斯康星州大学系统的所有校区。