Probing the Electronic State of Novel Materials using the Local Atomic Structure

利用局域原子结构探测新型材料的电子态

• 批准号: 0075149
• 负责人: Simon Billinge
• 金额: $ 33万
• 依托单位: Michigan State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-07-01 至 2004-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0075149&HistoricalAwards=false
• 关键词: Probing; Electronic; State; Novel; Materials

This condensed matter physics project focuses on the use of infrared and optical spectroscopy to study the dynamics of strongly correlated electron systems. From infrared reflectivity measurements one can obtain conductivity as a function of frequency and temperature, which relates to the two-particle electronic correlation function and provides fundamental input to the characterization of novel electronic systems. As industry moves toward higher speeds, smaller sizes and solutions incorporating novel materials, the relevance of strongly correlated systems to technology increases. Compound classes to be studied include ruthenium oxides in the Ruddlesden-Popper series, ytterbium compounds that exhibit or are close to an electronic phase transition, and doped Kondo semiconductors. By studying ruthenates, which are related to both cuprate and manganate transition-metal oxides, one can investigate the relationship between magnetism and unconventional charge transport (e.g. "bad metal behavior"). The Yb compounds in our research exhibit a phase diagram that includes heavy-fermion and mixed-valence phenomena, as well as an isostructural electronic phase transition. Research on these materials can help forge a link between the moment compensation physics of the periodic Anderson model and the phase transition dynamics of Mott-Hubbard systems. Undergraduate and graduate students involved in this work learn to carry out careful measurements utilizing modern equipment and receive valuable preparation for graduate school and employment in academic, industrial or government research.%%%This condensed matter physics project involves the characterization of strongly correlated electron systems. In such materials, interactions between electrons are very powerful and can induce electronic phenomena which are not yet understood. Strong electronic interactions can also induce new phases of matter and can lead scientists to new concepts of electron transport. These materials will play an increasingly significant role in emerging technologies: as industry moves toward higher speeds and smaller sizes and seeks solutions incorporating novel materials, the knowledge base from studies of strongly correlated systems becomes increasingly relevant. In this research, spectroscopic measurements of infrared, optical and ultra-violet reflectivity will be used to obtain conductivity as a function of frequency. Such measurements can reveal the fundamental electronic excitations in systems, including ruthenium oxides, which exhibit novel transport and magnetic phases; Ytterbium compounds, which manifest a phase transition at which the electronic valence changes from integer to non-integer values; and iron silicide, a small energy gap "Kondo" semiconductor with a very high dielectric coefficient at low frequency. Students involved in this research learn to think critically and to carry out careful measurements on modern equipment. For undergraduates this experience provides valuable preparation for graduate school; for graduate students, this training enhances their preparation for a career in teaching, industry or government research. In outreach efforts at K-12 schools with substantial underrepresented populations, the PI uses demonstrations of the phenomena of strongly correlated systems (e.g. magnetism and superconductivity) to embellish presentations on research and education and careers in science.

该凝聚态物理项目的重点是使用红外和光谱来研究密切相关的电子系统的动力学。从红外反射率测量中，可以获得与频率和温度有关的电导率，这与两粒子电子相关函数有关，并为新型电子系统的表征提供了基本输入。随着行业朝着更高的速度迈进，较小的尺寸和结合新材料的解决方案，紧密相关的系统与技术的相关性不断增加。要研究的化合物类别包括ruddlesden-popper系列中的含氟芬氧化物，展示或接近电子相变的YTTERBIUM化合物以及掺杂的Kondo半导体。通过研究与铜酸盐和锰酸盐过渡金属氧化物相关的鲜明情况，可以研究磁性和非常规电荷转运之间的关系（例如“不良金属行为”）。我们研究中的YB化合物展示了一个相图，其中包括重铁和混合价现象，以及同源性电子相变。对这些材料的研究可以帮助建立周期性安德森模型的瞬间补偿物理学与莫特 - 哈伯系统的相变动力学之间的联系。参与这项工作的本科生和研究生学会了利用现代设备进行仔细的测量，并在学术，工业或政府研究中为研究生院和就业提供宝贵的准备。%% %%此简洁的物理学项目涉及表征强相关的电子系统。在这样的材料中，电子之间的相互作用非常强大，并且可以诱导尚未理解的电子现象。强烈的电子相互作用也可以引起物质的新阶段，并可以使科学家达到电子传输的新概念。 这些材料将在新兴技术中发挥越来越重要的作用：随着行业向更高的速度和较小尺寸发展，并寻求结合新型材料的解决方案，从强度相关系统的研究中的知识基础变得越来越相关。在这项研究中，将使用红外，光学和超紫外反射率的光谱测量来获得电导率作为频率的函数。这样的测量可以揭示系统中的基本电子激发，包括氧化鱼，它们表现出新型的运输和磁相； ytterbium化合物，它表现出一种相变，在该相变，电子价从整数变为非全能值；和铁硅酸铁，一个小的能隙“ Kondo”半导体，低频时具有很高的介电系数。参与这项研究的学生学会了批判性的思考，并对现代设备进行仔细的测量。对于本科生，这种经验为研究生院提供了宝贵的准备；对于研究生，这项培训增强了他们为教学，行业或政府研究的职业做准备。 在大量代表性不足的K-12学校的推广工作中，PI使用了强度相关系统（例如磁性和超导性）现象的演示，以修饰有关科学研究，教育和职业的演讲。