Quantum Fluctuations and Broken Symmetries in Correlated Electron Systems

相关电子系统中的量子涨落和对称性破缺

• 批准号: 1004520
• 负责人: Sudip Chakravarty
• 金额: $ 38.1万
• 依托单位: University of California-Los Angeles
• 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=1004520&HistoricalAwards=false
• 关键词: Quantum; Fluctuations; Broken; Symmetries; Correlated

TECHNICAL SUMMARYThis award supports theoretical research and education on a variety of problems that are interlinked by the common threads of quantum fluctuations and broken symmetries when electronic correlations are important. This project will address: high temperature superconductivity in cuprates, dissipative quantum phase transitions in general, and in particular, in low dimensional systems such as nanowires, and the role of disorder in quantum phase transitions applicable to many condensed matter systems, from cuprates to heavy fermions to organics. The recent discovery of quantum oscillations in cuprate superconductors has ushered in a new era of this twenty-year old unsolved major problem in physics. A theoretical understanding of this phenomenon may result in a major breakthrough. The PI's approach is to model the various broken symmetry states, with particular attention paid to coexisting states of competing order parameters in the vortex liquid state. The PI will employ exact transfer matrix technique and Landauer-Pichard formula to compute Shubnikov-de Haas oscillations. Dissipative quantum phase transitions are addressed because of their potential importance in shedding light on the foundations of quantum mechanics, as well as their key role in a novel class of quantum criticality, with many applications. Numerical simulations as well as scaling theories will be used. A specific application of the theory is the ongoing experiments in quantum phase slips in nanowires. In the same broad framework, the PI will also investigate the role of disorder in phase transitions, in particular quantum phase transitions. Many complex materials of great importance in understanding correlated electron systems are inevitably rife with disorder. Both the tools of rigorous mathematical statistical mechanics as well as numerical simulations in well-defined quantum models will be addressed. There are many cases where some unorthodox thinking may be required; the notion of quantum mechanical entanglement entropy, the von Neumann entropy, is one of them. This award also supports training graduate students in theoretical condensed matter physics. Research activities will enhance teaching in undergraduate classes, where there are now many more minorities and women students. It is at this undergraduate level that the PI will encourage students to pursue careers in science.NONTECHNICAL SUMMARYThis award supports theoretical research and education on quantum phase transitions. These are an intensely studied phenomenon that has become cutting edge research in condensed matter physics. Ordinary phase transitions, like the transition of water to ice, take place at non-zero temperature and are driven by thermal fluctuations. Quantum phase transitions can take place at the absolute zero of temperature driven by the quantum fluctuations of Heisenberg's uncertainty principle. The PI aims to explore novel materials that have been discovered in recent years in this new light and to explain their observable, and so far puzzling, properties. This research may lead to further progress in predicting useful materials, such as materials that might exhibit superconductivity at room temperatures. Superconductivity is a quantum mechanical state of matter that so far occurs at low temperatures, at most about twice the frigid temperature where the element nitrogen, a gaseous component of our atmosphere, boils. Superconductors can carry electricity without loss. At the same time we would be learning fundamental aspects of quantum properties of matter. This research may lead to further understanding of novel materials that may form the foundations of future technologies.This award also supports training graduate students in theoretical condensed matter physics. Research activities will enhance teaching in undergraduate classes, where there are now many more minorities and women students. It is at this undergraduate level that the PI will encourage students to pursue careers in science.

技术总结该奖项支持对各种问题的理论研究和教育，当电子关联很重要时，这些问题通过量子涨落和对称性破缺的共同线索相互关联。这个项目将解决：铜酸盐中的高温超导，一般的耗散量子相变，特别是在诸如纳米线这样的低维系统中，以及无序在适用于许多凝聚态系统的量子相变中的作用，从铜酸盐到重费米子再到有机物。最近在铜酸盐超导体中发现量子振荡，开启了这个二十年来一直悬而未决的物理学重大问题的新纪元。对这一现象的理论理解可能会带来重大突破。PI的方法是模拟各种破缺对称态，特别注意涡旋液态中竞争序参数的共存态。PI将使用精确转移矩阵技术和Landauer-Pichard公式来计算Shubnikov-de Haas振荡。耗散量子相变之所以被讨论，是因为它们在量子力学的基础上具有潜在的重要性，以及它们在一类新的量子临界性中的关键作用，具有许多应用。将使用数值模拟和比例理论。该理论的一个具体应用是正在进行的纳米线中量子相移的实验。在同样广泛的框架内，PI还将研究无序在相变中的作用，特别是量子相变。许多复杂的材料对理解相关的电子系统非常重要，它们不可避免地充斥着无序。这两个工具，严格的数学统计力学，以及数值模拟的明确定义的量子模型将被讨论。在许多情况下，可能需要一些非正统的思考；量子力学纠缠熵的概念，即冯·诺依曼熵，就是其中之一。该奖项还支持对研究生进行理论凝聚态物理的培训。研究活动将加强本科班级的教学，目前本科班级中有更多的少数民族和女性学生。正是在这个本科水平，PI将鼓励学生追求科学方面的职业生涯。非技术总结这个奖项支持量子相变的理论研究和教育。这些都是一个被深入研究的现象，已经成为凝聚态物理学的前沿研究。普通的相变，如水到冰的转变，发生在非零温度下，由热波动驱动。在海森堡测不准原理的量子涨落驱动下，在绝对零度温度下可以发生量子相变。PI旨在以这种新的视角探索近年来发现的新材料，并解释它们的可观察到的、迄今令人困惑的性质。这项研究可能会在预测有用的材料方面取得进一步的进展，例如在室温下可能表现出超导电性的材料。超导性是物质的一种量子力学状态，到目前为止，这种状态发生在低温下，最多是我们大气中的气体成分氮元素沸腾的严寒温度的两倍。超导体可以无损耗地输送电能。与此同时，我们将学习物质量子性质的基本方面。这项研究可能导致对可能构成未来技术基础的新材料的进一步理解。该奖项还支持对研究生进行理论凝聚态物理方面的培训。研究活动将加强本科班级的教学，目前本科班级中有更多的少数民族和女性学生。正是在这一本科水平，PI将鼓励学生追求科学职业生涯。