Thermoelectric and Thermal Transport in Disordered and Strongly Correlated Electron Systems

无序和强相关电子系统中的热电和热传输

• 批准号: 1006752
• 负责人: Alexander Finkelstein
• 金额: $ 28.5万
• 依托单位: Texas A&M Research Foundation
• 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: 2010-10-01 至 2014-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1006752&HistoricalAwards=false
• 关键词: Thermoelectric; Thermal; Transport; Disordered; Strongly

TECHNICAL SUMMARYThis award supports theoretical research of thermoelectric and thermal transport in various systems, for which an essential fraction of the entropy is stored in an ensemble of collective modes. These modes complement quasi-particle excitations and describe different kinds of critical fluctuations. Generally, promising candidate systems for displaying large thermopower are those in which strong fluctuations invalidate the regular Sommerfeld expansion used for finding thermal properties at low temperatures.As a theoretical tool, a newly developed scheme based on quantum kinetic equations will be applied, thereby profiting from the recent experience of the PI in studying the Nernst effect in superconductors. Analysis of the Nernst effect showed that thermal transport can be a more effective tool for studying fluctuation effects than the ordinary electronic transport. The generality of the method makes it possible to account for different kinds of electron-electron interactions mediated by critical fluctuations. The research will enhance the theoretical understanding of thermal transport in systems which exhibit non-Fermi liquid behavior. The issues to be addressed theoretically include thermopower near the metal-insulator transition caused by disorder in combination with electron-electron interactions, and near quantum phase transitions in systems of itinerant electrons. As a result, the research will help to develop a conceptual picture of thermoelectric transport in the vicinity of a quantum critical point or the metal-insulator transition. In particular, it may result in a new simple formula for the thermopower determined by fluctuations that can be used in place of Mott's formula. The fundamental understanding of thermoelectricity in strongly interacting systems acquired in this research will help to make informed choices in the quest for materials with strong thermopower. Such materials can be used for creating new coolers, which are needed for progress in low temperature experimental physics and applied instrumentation.Training junior researchers is of paramount importance in any academic setting. Besides physics of thermal phenomena, the participation in the research will provide training of the young scientists in advanced methods of condensed matter theory and quantum kinetics.NON-TECHNICAL SUMMARYThis award supports theoretical research on the flow of heat and electric charge in certain materials for which contributions from electrons dominate heat flow. The PI will use advanced theoretical techniques to investigate particularly interesting cases, including: (1) materials that are near a transformation from a metal to an insulator due to impurities and imperfections and strong interactions between electrons, and(2) materials that are near a quantum phase transition. Unlike an ordinary phase transition which is driven by thermal fluctuations, for example the transition from ice to water at 32 degrees, a quantum phase transition is driven by the quantum fluctuations of Heisenberg's famous uncertainty principle and can occur at the absolute zero of temperature, a frigid -460 degrees on the familiar Fahrenheit scale. (3) a gas of electrons confined to two dimensions which can be created in artificial semiconductor material structures,(4) spin liquids which are predicted to arise in certain materials where the interactions between electrons cannot all be simultaneously satisfied. Naively, one might think these materials will become magnets, but rather these frustrated interactions lead to a liquid-like state of electrons without magnetic order. The PI will use quantum mechanical equations that can describe the net movement of electrons in states out of equilibrium, such as when there is a difference of temperature across a material. This research will advance our understanding of the transport of heat and charge in materials with strongly interacting electrons which exhibit new states of electronic matter or interesting phenomena. The PI's research may lead to an interesting way to probe the properties of materials and new states of electronic matter. The fundamental understanding of thermoelectricity in strongly interacting systems acquired in this research will help to make informed choices in the quest for materials with strong thermopower. The thermopower is a measure for the temperature difference developing in a sample when a voltage difference is maintained between the contacts. This is why such materials can be used for creating new cooling devices which have a wide range of potential technological applications.Training junior researchers is of paramount importance in any academic setting. Besides physics of thermal phenomena, the participation in the research will provide training of the young scientists in advanced methods of condensed matter theory and quantum kinetics.

该奖项支持各种系统中热电和热传输的理论研究，其中熵的重要部分存储在集体模式的集合中。这些模式补充准粒子激发和描述不同种类的临界波动。一般来说，有希望的候选系统，显示大的热电势是那些强烈的波动无效的定期索末菲膨胀用于寻找在低温下的热性质作为一种理论工具，一个新开发的计划的基础上，量子动力学方程将被应用，从而受益于最近的经验，PI在研究能斯特效应的超导体。对能斯特效应的分析表明，热输运是研究涨落效应的一个比普通电子输运更有效的工具。该方法的通用性使得有可能考虑不同类型的电子-电子相互作用介导的临界波动。这一研究将加深对非费米液体热输运的理论理解。理论上要解决的问题包括由无序结合电子-电子相互作用引起的金属-绝缘体转变附近的热电势，以及巡回电子系统中的近量子相变。因此，这项研究将有助于发展一个概念性的图片热电输运在附近的量子临界点或金属-绝缘体转变。特别是，它可能会导致一个新的简单公式的热功率确定的波动，可以用来代替莫特的公式。在这项研究中获得的强相互作用系统中热电的基本理解将有助于在寻求具有强热电性的材料时做出明智的选择。这些材料可用于制造新的冷却器，这是低温实验物理学和应用仪器发展所必需的。在任何学术环境中，培训初级研究人员都是至关重要的。除了热现象物理学之外，参与研究还将为年轻科学家提供凝聚态理论和量子动力学先进方法的培训。非技术总结该奖项支持对某些材料中的热流和电荷流的理论研究，其中电子的贡献占热流的主导地位。PI将使用先进的理论技术来研究特别有趣的情况，包括：（1）由于杂质和缺陷以及电子之间的强相互作用而接近从金属到绝缘体转变的材料，以及（2）接近量子相变的材料。不同于由热涨落驱动的普通相变，例如在32度时从冰到水的转变，量子相变由海森堡著名的不确定性原理的量子涨落驱动，并且可以发生在绝对零度，即熟悉的华氏温度范围内的寒冷-460度。(3)限制在两个维度的电子气体，其可以在人造半导体材料结构中产生，（4）自旋液体，其被预测在电子之间的相互作用不能同时满足的某些材料中产生。人们可能会天真地认为这些材料会成为磁铁，但这些受挫的相互作用会导致电子处于没有磁序的液体状态。PI将使用量子力学方程来描述电子在平衡状态下的净运动，例如当材料之间存在温差时。这项研究将促进我们对具有强相互作用电子的材料中的热和电荷的传输的理解，这些材料表现出电子物质的新状态或有趣的现象。PI的研究可能会导致一种有趣的方式来探测材料的性质和电子物质的新状态。在这项研究中获得的强相互作用系统中热电的基本理解将有助于在寻求具有强热电性的材料时做出明智的选择。热电势是当触点之间保持电压差时样品中产生的温差的量度。这就是为什么这种材料可以用于创造具有广泛潜在技术应用的新冷却设备。培训初级研究人员在任何学术环境中都是至关重要的。除了热现象物理学之外，参与研究还将为年轻科学家提供凝聚态理论和量子动力学先进方法的培训。