Interplay Between Superconductivity and Charge Order in Near-Critical Metals

近临界金属中超导性和电荷顺序之间的相互作用

• 批准号: 1523036
• 负责人: Andrey Chubukov
• 金额: $ 31.79万
• 依托单位: University of Minnesota-Twin Cities
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-01 至 2019-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1523036&HistoricalAwards=false
• 关键词: Interplay; Between; Superconductivity; Charge; Order

NONTECHNICAL SUMMARYThis award supports theoretical research and education in condensed matter physics, in the subfield of high temperature superconductivity. At sufficiently low temperature, high temperature superconductors become superconducting, a cooperative state of electrons that exhibits distinctly different properties from those of ordinary conductors like copper. Among them is the ability to conduct electricity without dissipation. This theoretical investigation is inspired by experimental discoveries over the last few years indicating that the highest temperature at which superconductivity appears is often the largest near a boundary between other kinds of electronic states for which the electrons self organize to display periodic arrangements of either electron magnetism or electron charges. The understanding of how the competition among distinctly different tendencies for electrons to self-organize might enhance the tendency for superconductivity is important in developing a fundamental understanding of the origin of high temperature superconductivity. It may also contribute to developing the capability to design new superconducting materials which exhibit superconductivity at higher temperatures and have properties that make them suitable for practical applications. This award supports a detailed study of what causes charge and magnetic orders to compete and how superconductivity gains from this competition. This project supports specialized training of graduate students and postdoctoral researchers in an active area of research, as well as community discussions of the science that enables high temperature superconductivity.TECHNICAL SUMMARYThis project supports theoretical research and education in the field of strongly correlated electron systems. The research is focused on two fundamental issues related to the pseudo gap in systems of fermions tuned to a quantum-critical point: 1. the competition between d-wave superconductivity and competing non-superconducting orders, and 2. the analysis of superconducting fluctuations when superconductivity emerges from a quantum-critical regime and the normal state is very different from that of a Fermi liquid. The PI will investigate two competing orders: incommensurate charge density wave order and incommensurate pair density wave order. The latter can be considered as superconductivity with a non-zero total momentum of a pair. The PI and his research team will analyze the stability of competing orders, ordering patterns, and whether critical fluctuations of competing orders give an additional boost to superconductivity leading to transition temperatures above the corresponding quantum-critical points. In the analysis of superconducting fluctuations, the PI and his team will study in detail the effects of longitudinal fluctuations of a superconducting order parameter in a situation when superconductivity emerges from a quantum-critical regime in which a pairing potential couples incoherent fermions. The goal of this study is to go beyond conventional Eliashberg-type theories to obtain the full Luttinger-Ward functional, and analyze the profile of fluctuations away from the minimum and check the existence of an intermediate temperature range where the gap is already developed, but gap fluctuations keep fermions incoherent and prevent a true superconducting order to develop. In this temperature range the system will display the pseudogap behavior. The interplay between superconductivity and competing orders is a pervasive theme in the study of classes of exotic superconductors, such as the heavy fermion, cuprate, ruthenate, Fe-pnictide, organic and molecular superconductors. Magnetism and superconductivity are antithetical in elemental superconductors, but in exotic superconductors magnetism may enhance the tendency toward superconductivity. The analysis of the full phase diagram of quantum-critical metals may help advance understanding of the key ingredients required for high- temperature superconductivity in correlated electron systems.

非技术总结该奖项支持凝聚态物理学的理论研究和教育，在高温超导的子领域。在足够低的温度下，高温超导体变成超导体，这是一种电子的合作状态，表现出与铜等普通导体明显不同的性质。其中之一是导电而不耗散的能力。这一理论研究的灵感来自于过去几年的实验发现，这些发现表明，出现超导性的最高温度通常是在其他类型的电子状态之间的边界附近最大的，对于这些电子状态，电子自组织以显示电子磁性或电子电荷的周期性排列。 理解电子自组织的明显不同倾向之间的竞争如何增强超导性的倾向，对于发展高温超导性起源的基本理解是重要的。它还可能有助于发展设计新的超导材料的能力，这些材料在更高的温度下表现出超导性，并具有使它们适合实际应用的特性。 该奖项支持详细研究导致电荷和磁序竞争的原因以及超导性如何从这种竞争中获益。本项目支持研究生和博士后研究人员在活跃的研究领域的专业培训，以及社区讨论的科学，使高温超导性。技术概述本项目支持强关联电子系统领域的理论研究和教育。 研究的重点是两个基本问题有关的赝能隙系统的费米子调谐到量子临界点：1。d波超导性与竞争性非超导有序之间的竞争，以及2.当超导性从量子临界状态出现时，超导涨落的分析，正常状态与费米液体的状态非常不同。PI将研究两个竞争秩序：无公度电荷密度波秩序和无公度对密度波秩序。后者可以被认为是具有非零总动量对的超导性。 私家侦探和他的研究小组 将分析竞争秩序的稳定性，有序模式，以及竞争秩序的临界波动是否会额外提高超导性，导致转变温度高于相应的量子临界点。 在超导波动的分析中，PI和他的团队将详细研究超导序参量的纵向波动的影响，当超导性从量子临界状态出现时，配对势耦合非相干费米子。本研究的目标是超越传统的Eliashberg型理论，以获得完整的Luttinger-Ward泛函，并分析远离最小值的波动轮廓，并检查是否存在一个中间温度范围，其中差距已经发展，但间隙波动保持费米子不相干，并防止真正的超导秩序的发展。在此温度范围内，系统将显示赝能隙行为。超导性和竞争有序之间的相互作用是研究奇异超导体的一个普遍主题，例如重费米子，铜酸盐，铁酸盐，铁磷族元素化物，有机和分子超导体。在元素超导体中，磁性和超导性是对立的，但在奇异超导体中，磁性可能会增强超导性的趋势。对量子临界金属的完整相图的分析可能有助于促进对相关电子系统中高温超导性所需关键成分的理解。