Quantum Phase Transitions in Spin Systems

自旋系统中的量子相变

• 批准号: 9623181
• 负责人: Subir Sachdev
• 金额: $ 35.2万
• 依托单位: Yale University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-05-15 至 2002-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9623181&HistoricalAwards=false
• 关键词: Quantum; Phase; Transitions; Spin; Systems

9623181 Sachdev The primary objective in this grant is to undertake a systematic theoretical study of the finite temperate properties of quantum spin systems. The project brings together a wide variety of problems from apparently diverse systems. For example the cuprate compounds, also known as high Tc superconductors, at low doping levels manifest complicated interplay between antiferromagnetic fluctuations and quenched disorder. NMR in Quantum Hall effect systems shows novel spin correlations. Apart from these principal examples, there are properties of rare earth intermetallics where the magnetic ground states are critically influenced by disorder or competing energy scales. Finally there are anisotropic materials where spin exchange and conduction occur primarily along one direction. All of this work will be carried out in the framework of a quantum field theory, derived from a continuum description of the spins. %%% The storm generated by the discovery of high Tc superconductivity led, rather early, to the solution of an old problem, that of quantum antiferromagnets. The PI was responsible for some of the major developments and is now proposing to extend that work to a variety of other problems, specifically involving finite temperature effects. The applications are in lightly doped compounds (which show how magnetism is destroyed by doping) and their temperature dependent properties. ***

9623181 SACHDEV这笔赠款的主要目标是对量子自旋系统的有限温带特性进行系统的理论研究。 该项目汇集了来自不同系统的各种问题。 例如，低掺杂水平的铜酸盐化合物（也称为高TC超导体）在抗磁性波动和淬火障碍之间表现出复杂的相互作用。 量子大厅效应系统中的NMR显示出新的自旋相关性。 除了这些主要示例外，还有稀土金属层的特性，其中磁接地状态受到无序或竞争能量尺度的严重影响。 最后是各向异性材料，其中自旋交换和传导主要沿一个方向发生。 所有这项工作将在量子场理论的框架内进行，该理论源自对旋转的连续描述。 %% %%通过发现高的TC超导性产生的风暴导致了旧问题的解决方案。 PI负责一些主要发展，现在建议将其扩展到其他各种问题，特别是涉及有限温度效应。 这些应用是在轻度掺杂的化合物中（显示磁性如何被掺杂破坏）及其温度依赖性特性。 ***