Dynamic Correlations in Strongly Fluctuating Condensed Matter

强波动凝聚态物质的动态相关性

• 批准号: 0306940
• 负责人: Collin Broholm
• 金额: $ 46万
• 依托单位: Johns Hopkins University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-07-15 至 2007-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0306940&HistoricalAwards=false
• 关键词: Dynamic; Correlations; Strongly; Fluctuating; Condensed

Strongly fluctuating solids are interesting because their properties are anomalous, potentially useful, and difficult to predict. Based on inelastic neutron scattering, this experimental project will providedetailed information about dynamic correlations in such materials leading to progress in understanding and predicting their cooperative behavior. The materials to be studied are (i) Well-defined model systemslinked to recent developments in condensed matter theory. Examples include spin ladders with a field induced quantum phase transition and an extended high field quantum critical phase. (ii) Magnetic materialsdisplaying unusual phenomena that cannot be described satisfactorily with existing theories. Examples include oxides and organic materials where exchange interactions do not favor static long range spin order.(iii) Materials where fluctuations affect possibilities for future technological applications. Examples include assemblies of ferro-magnetic nano-wires where transverse standing spin waves and inter-wire correlations will be probed. The scientific projects will be the basis for an educational program for students and post doctoral fellows. They will learn to apply innovative neutron scattering technique to modern problems in condensed matter physics thus preparing them to be major scientific contributors to the spallation neutronsource. Many applications of materials rely on or are severely affected by random atomic scale motion called fluctuations. This is increasingly true in nano-technology where device dimensions are reduced towards theatomic spacing. Materials properties linked to fluctuations are at present difficult to predict. Therefore experiments such as those proposed here are the key to progress. To probe motion on the atomic scale the project will use the powerful inelastic neutron scattering technique. Careful analysis of the pattern of neutron scattering from a sample reveals detailed information about spatial and temporal correlations between the atoms that make up the solid. Prototypical magnetic materials that are strongly affected by fluctuations will be the focus of the experiments. These include so-called spin-ladders where quantum fluctuations can be tuned through the application of a strong magnetic field, frustrated magnetic systems that fail to order due to competing interactions, and ferro-magnetic nano-wires with anomalous spin wave propagation. Education will be an integral part of the project where students and post doctoral fellows will carry out experiments using cutting edge instrumentation and analysis under the guidance of the principal investigator. The goal is to educate creative experimental physicists with expertise in the application of neutron scattering to materials science. This is crucial as the nation invests $1.4B in the worlds most advanced neutron scattering facility at Oak Ridge National Laboratory.

强波动固体是有趣的，因为它们的性质是异常的，潜在的有用的，并且难以预测。基于非弹性中子散射，该实验项目将提供有关此类材料动态相关性的详细信息，从而在理解和预测其合作行为方面取得进展。要研究的材料是(i)与凝聚态理论的最新发展相联系的定义良好的模型系统。实例包括具有场诱导量子相变和扩展高场量子临界相的自旋阶梯。（ii）磁性材料表现出用现有理论不能令人满意地描述的不寻常现象。例子包括氧化物和有机材料，它们的交换相互作用不利于静态的长距离自旋顺序。（三）波动影响未来技术应用可能性的材料。例子包括铁磁纳米线组件，其中横向驻波和线间相关性将被探测。这些科学项目将成为学生和博士后教育计划的基础。他们将学习将创新的中子散射技术应用于凝聚态物理中的现代问题，从而使他们成为散裂中子源的主要科学贡献者。材料的许多应用依赖于或受到称为波动的随机原子尺度运动的严重影响。这在纳米技术中越来越真实，在纳米技术中，器件尺寸减小到原子间距。与波动有关的材料性质目前难以预测。因此，这里提出的这些实验是取得进展的关键。为了在原子尺度上探测运动，该项目将使用强大的非弹性中子散射技术。对样品中中子散射模式的仔细分析揭示了构成固体的原子之间空间和时间相关性的详细信息。受波动强烈影响的典型磁性材料将是实验的重点。其中包括所谓的自旋阶梯，量子涨落可以通过强磁场的应用来调节，由于竞争相互作用而无法有序的受挫磁系统，以及具有异常自旋波传播的铁磁纳米线。教育将是项目的一个组成部分，学生和博士后研究员将在首席研究员的指导下使用尖端仪器和分析进行实验。目标是培养具有创造性的实验物理学家，在中子散射应用于材料科学方面具有专业知识。这是至关重要的，因为国家在橡树岭国家实验室投资了14亿美元，用于世界上最先进的中子散射设备。