Transport, Magnetism and Superconductivity in Strongly Correlated and Frustrated Lattices

强相关和受抑晶格中的输运、磁性和超导

• 批准号: 0408247
• 负责人: Sriram Shastry
• 金额: $ 27万
• 依托单位: University of California-Santa Cruz
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-08-15 至 2008-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0408247&HistoricalAwards=false
• 关键词: Transport; Magnetism; Superconductivity; Strongly; Correlated

This award supports theoretical research and education in the area of strongly correlated electron materials. The PI will carry out theoretical research to study transport, magnetic and superconducting behavior in highly frustrated lattices. This work is motivated by very recent discoveries of magnetism and unusual superconductivity below ~5 K, and of anomalous transport behavior in the sodium cobalt oxide system Na_xCoO2. These metallic systems display a thermopower as large as some of the best semiconductors; the thermopower is also strongly magnetic field dependent. The Hall effect is most unusual in that there is no saturation with temperature. Extreme type II superconductivity occurs on hydration. Unusual magnetic long-ranged order occurs in the phase diagram. Experimental findings such as these challenge the tenets of the basic theory of metals, suggesting an important role for strong many-body correlations in these systems. The PI will use a combination of analytical and numerical techniques applied to appropriate models to study the transport properties and the occurrence, as well as the nature, of the magnetic and superconducting states. The research will focus on the especially strong many-body renormalizations revealed by recent experiments.Broader impacts: Studying the cobaltates may ultimately improve our understanding of other strongly correlated electron systems, such as the high temperature superconductors, which have proven to be very intellectually challenging. The cobaltates are potentially very important from a technological point of view in their own right - their large thermopower combined with low resistance enables them to achieve the best-known figure of merit at high temperature. They are also related to the lighter alkali atom cobaltate LixCoO2 that is central to lightweight lithium battery technology. Materials such as Liy-xNaxCoO2, that arise as natural possibilities in this study, may catalyze a novel fusion of thermoelectric and battery technologies leading to new technologies. This award also supports graduate level education in advanced theoretical condensed matter physics. %%%This award supports theoretical research and education on strongly correlated electron materials with a focus on understanding the anomalous properties and ordered states revealed in recent experiments on cobaltite compounds, Na_xCoO_2. These experiments show that the cobaltites are unlike ordinary metals. They also show unusual magnetic and superconducting states. It is believed that the inability of the interactions between electron spins to be satisfied because of the geometry of the underlying crystal structure (geometric frustration) combined with strong interactions among electrons, leads to the anomalous properties exhibited by these materials. Some properties of these strongly correlated electron materials, like their combined large thermopower and low resistance, suggest potential technological applications and the potential for new technologies, as suggested above. The study of these materials, like other strongly correlated-electron materials, leads to the discovery of new fundamental condensed matter physics. This award also supports graduate level education in advanced theoretical condensed matter physics. ***

该奖项支持强相关电子材料领域的理论研究和教育。PI将进行理论研究，研究高度受挫晶格中的输运、磁性和超导行为。这项工作的动机是最近发现的磁性和~ 5k以下的异常超导性，以及Na_xCoO2氧化钴钠系统的异常输运行为。这些金属系统显示出与一些最好的半导体一样大的热功率；热电也强烈依赖于磁场。霍尔效应是最不寻常的，因为它不随温度饱和。极端II型超导性发生在水合作用下。相图中出现不寻常的磁长程顺序。诸如此类的实验发现挑战了金属基本理论的原则，表明这些系统中强多体相关性的重要作用。PI将使用分析和数值技术相结合的方法，应用于适当的模型来研究磁性和超导态的输运性质、发生以及性质。研究将集中在最近实验揭示的特别强的多体重整化。更广泛的影响：研究钴酸盐可能最终提高我们对其他强相关电子系统的理解，例如高温超导体，这已被证明是非常具有智力挑战性的。从技术的角度来看，钴酸盐本身是非常重要的——它们的大热功率和低电阻相结合，使它们能够在高温下获得最著名的性能。它们还与较轻的碱原子钴酸盐LixCoO2有关，LixCoO2是轻量化锂电池技术的核心。在这项研究中，Liy-xNaxCoO2等材料作为自然可能性出现，可能催化热电和电池技术的新型融合，从而产生新技术。该奖项还支持高级理论凝聚态物理的研究生水平教育。该奖项支持强相关电子材料的理论研究和教育，重点是理解钴酸盐化合物Na_xCoO_2最近实验中揭示的异常性质和有序态。这些实验表明，钴酸盐不同于普通金属。它们还表现出不同寻常的磁性和超导态。人们认为，由于晶体结构的几何特性（几何挫折）和电子之间的强相互作用，电子自旋之间的相互作用无法得到满足，导致了这些材料表现出的异常性质。如上所述，这些强相关电子材料的一些特性，如其大热功率和低电阻的结合，表明了潜在的技术应用和新技术的潜力。对这些材料的研究，就像其他强相关电子材料一样，导致了新的基本凝聚态物理的发现。该奖项还支持高级理论凝聚态物理的研究生水平教育。＊＊＊