Dynamics of Quantum Magnets and Superconductors

量子磁体和超导体的动力学

• 批准号: 0098226
• 负责人: Subir Sachdev
• 金额: $ 46万
• 依托单位: Yale University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-05-01 至 2005-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0098226&HistoricalAwards=false
• 关键词: Dynamics; Quantum; Magnets; Superconductors

This award supports theoretical research on fundamental questions raised by experiments on the magnetic and charge transport properties of complex oxide compounds. The aim of this work is to elucidate the competition between the many possible ground states of correlated electron systems in low dimensions, the quantum phase transitions between them, and the complex crossovers in their dynamic and transport properties at finite temperature. One focus of this work will be the response of correlated quantum systems to non-magnetic impurities like Zn or Li. Nuclear magnetic resonance, neutron scattering, and tunneling microscopy experiments have shown that such impurities can be sensitive probes of the quantum state of the electrons. The PI plans to explore whether these probes can distinguish among the different models proposed for high temperature superconductors. The PI's recent theories correlate the results of different experimental probes and suggest new experiments and open new theoretical issues that will be investigated. The spectrum of collective spin-singlet and spin-triplet excitations in d-wave superconductors, the manner in which these excitations couple to the fermionic S=1/2 quasiparticle excitations, and their possible interplay with "stripe" correlations will also be studied. The PI also plans to pursue related projects on spin-glass order in strongly disordered transition metal and rare earth compounds, and tunneling between lateral quantum Hall edge states.%%%This award supports theoretical research on fundamental questions raised by experiments on the magnetic and charge transport properties of high temperature superconductors and related transition metal oxide compounds. The proposal involves using impurities like Zn or Li as probes of the quantum state of the electrons in these systems. The response of the correlated electron system as revealed by a variety of experiments is expected to elucidate the fundamental nature of magnetic and superconducting states in these materials. These states are both a puzzle and a motivation for theoretical and experimental work that challenges our fundamental concepts of superconducting, magnetic, and metallic states. A unifying theme of the proposed research involves exploring the role of quantum phase transitions in determining macroscopic properties and the nature of electronic excitations in high temperature superconductors and related transition metal oxides at finite temperature. Quantum phase transitions occur at zero temperature in response to small changes in an external parameter. The proposed work also supports graduate education in state-of-the art methods in condensed matter theory.***

该奖项支持对复杂氧化物化合物的磁性和电荷传输特性实验所提出的基本问题的理论研究。 本工作的目的是阐明在低维相关电子系统的许多可能的基态之间的竞争，它们之间的量子相变，以及在有限温度下的动力学和输运性质的复杂交叉。 这项工作的一个重点将是相关量子系统对非磁性杂质（如Zn或Li）的响应。 核磁共振、中子散射和隧道显微镜实验表明，这些杂质可以作为电子量子态的灵敏探针。PI计划探索这些探针是否可以区分高温超导体的不同模型。 PI最近的理论将不同实验探测的结果相关联，并提出了新的实验和将被研究的新的理论问题。 集体自旋单重态和自旋三重态激发在d波超导体的频谱，这些激发耦合到费米S=1/2准粒子激发的方式，以及它们与“条纹”相关性的可能相互作用也将被研究。PI还计划在强无序过渡金属和稀土化合物中进行自旋玻璃有序的相关项目，以及横向量子霍尔边缘态之间的隧道效应。该奖项支持对高温超导体和相关过渡金属氧化物化合物的磁性和电荷传输特性实验所提出的基本问题的理论研究。该提案涉及使用Zn或Li等杂质作为这些系统中电子量子态的探针。 相关电子系统的响应所揭示的各种实验，预计将阐明这些材料中的磁性和超导态的基本性质。这些状态既是一个难题，也是理论和实验工作的动力，挑战了我们对超导，磁性和金属状态的基本概念。拟议研究的一个统一主题涉及探索量子相变在确定宏观性质中的作用以及高温超导体和相关过渡金属氧化物在有限温度下的电子激发性质。量子相变发生在零温度响应于外部参数的微小变化。拟议的工作还支持凝聚态理论中最先进方法的研究生教育。