Multipolar Orders and Interplay with Hybridization in non-Kramers Kondo Lattice Materials

非 Kramers Kondo 晶格材料中的多极有序及其与杂化的相互作用

• 批准号: 1917511
• 负责人: Andriy Nevidomskyy
• 金额: $ 34.5万
• 依托单位: William Marsh Rice University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-05-01 至 2023-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1917511&HistoricalAwards=false
• 关键词: Multipolar; Orders; Interplay; Hybridization; non

I. Nontechnical SummaryOver the past decades, intensive research in condensed matter physics has focused on materials with strong electron correlations. These materials behave differently from ordinary metals such as aluminum or copper because the electrically charged particles of which they consist do not always behave like “ordinary” electrons. For instance, when an electric current or thermal heat flow travels through an ordinary metal, the electrons move independently and interact only very weakly with each other. However when a current travels through a metal that has strong electron correlations, the electrons lose their individuality and form collective excitations, compelling researchers to call them “strange metals.” A classical example of a collective behavior is the complex pattern of a flying flock of birds, seemingly behaving as one unit despite comprising thousands of individual birds. A fascinating class of “strange metals” is realized in the Kondo lattice materials, so named in honor of the Japanese physicist Jun Kondo who first explained the mechanism behind the unusual electric current flow in materials of this type. While the theoretical underpinnings of the Kondo effect, in its simplest form, were explained in the 1970s, a recent discovery of a novel class of Kondo materials based on the chemical element praseodymium has puzzled scientists. The electrons in these materials are forced to choose between two kinds of collective behavior — as if birds in the above example were forced to choose between two different “flocks” traveling in different directions. In the materials that are subject of this research, one direction leads to an emergent order in the shape of praseodymium orbitals, while the other results in electrons forming a “strange metal” whose properties are not yet well understood. The proposed research will elucidate the nature of these collective behaviors, including superconductivity, using a toolbox of innovative theoretical and computational methods. If successful, the proposed research has the potential to significantly advance the state of the art in the field and improve our understanding of the fundamental aspects of the “strange metal” behavior in these materials.This project also seeks to integrate educational and outreach activities with the fundamental research. Recognizing the national need for high-quality, well-informed career mentoring for graduate students in the physical sciences, the principal investigator will organize a series of workshops to train faculty in how best to provide this kind of mentoring. These biennial COMPASS (Career and Occupational Mentoring for the Professional Advancement of Science Students) workshops will introduce faculty to career planning and mentoring resources and prepare them to implement effective graduate student mentoring at their institutions. It is hoped that such robust mentoring will help adequately prepare science graduate students to translate their technical knowledge into skills needed across the full range of STEM-related careers. The need for such efforts is recognized nationwide, and with the NSF’s support, we hope to make this series of workshops available to faculty at as many institutions as possible. II. Technical SummaryOver the past decades, intensive research in condensed matter physics has focused on materials with strong electron correlations. Kondo lattice materials containing f-shell elements are a class of strongly correlated electron systems with a rich history, and the key challenge is to understand the interplay between magnetic ordering of the local f-moments and their hybridization with the conduction electrons. In this research, we focus on elucidating the solution for a specific type of Kondo lattice problem whose ions, such as praseodymium 3+, contain an even number of f-electrons, with a ground state that is a non-Kramers doublet. A recent discovery of a family of such materials, in particular PrV2Al20 and PrTi2Al20, has shown very rich behavior, including unusual quadrupolar magnetism, a non-Fermi liquid metal phase, and unconventional superconductivity.Intellectual Merit: To date, most of the theoretical research on non-Kramers f-ions has focused on either the nature of the quadrupolar ordering, or on the effectively mean-field description of the multi-channel Kondo effect, which occurs when the non-Kramers doublet is screened by conduction electrons. The principal intellectual merit of this proposal is to combine these two aspects in an integral way, aiming to answer the questions of how the magnetic multipolar order gets suppressed by the Kondo hybridization; what the nature of the quantum critical point is and how the observed non-Fermi liquid behavior arises; and what the nature of the superconductivity is. Importantly, the proposed research will go beyond the mean-field description of the multipolar order to include the effect of quantum fluctuations, and will employ advanced analytical and numerical techniques to elucidate the effect of Kondo hybridization beyond what has been done previously. If successful, the proposed research has the potential to significantly advance the state of the art in the field and improve our understanding of the fundamental aspects of strong electron interactions in these materials.Broader Impacts: Recognizing the national need for high-quality, well-informed career mentoring for graduate students in the physical sciences, we propose to organize a series of biennial COMPASS (Career and Occupational Mentoring for the Professional Advancement of Science Students) workshops that will introduce faculty to career planning and mentoring resources, provide them with descriptions of how to use these resources, and prepare them to formulate concrete action plans to implement graduate student mentoring at their institutions. It is hoped that such robust mentoring will help adequately prepare science graduate students to translate their technical knowledge into skills needed across the full range of STEM-related careers. The need for such efforts is recognized nationwide, and with the NSF’s support, we hope to make this series of workshops available to faculty at as many institutions as possible.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

在过去的几十年里，凝聚态物理的深入研究集中在具有强电子相关性的材料上。这些材料的行为不同于普通金属，如铝或铜，因为它们组成的带电粒子并不总是表现得像“普通”电子。例如，当电流或热流通过普通金属时，电子独立运动，彼此之间的相互作用非常弱。然而，当电流穿过具有强电子相关性的金属时，电子失去了它们的个性并形成集体激发，迫使研究人员称它们为“奇怪的金属”。集体行为的一个经典例子是鸟群飞行的复杂模式，尽管由数千只鸟组成，但它们的行为似乎是一个整体。在近藤晶格材料中实现了一类迷人的“奇怪金属”，这样命名是为了纪念日本物理学家近藤俊，他首先解释了这种材料中不寻常的电流流动背后的机制。虽然“近藤效应”最简单的理论基础在20世纪70年代就得到了解释，但最近发现的一类基于化学元素镨的新型近藤材料却让科学家们感到困惑。这些材料中的电子被迫在两种集体行为中做出选择——就像上面例子中的鸟被迫在两个不同方向飞行的不同“鸟群”中做出选择一样。在这项研究的主题材料中，一个方向导致镨轨道形状的紧急顺序，而另一个方向导致电子形成一种性质尚不清楚的“奇怪金属”。提出的研究将阐明这些集体行为的本质，包括超导性，使用创新的理论和计算方法的工具箱。如果成功的话，这项研究有可能大大提高该领域的技术水平，并提高我们对这些材料中“奇怪金属”行为的基本方面的理解。该项目还寻求将教育和外联活动与基础研究结合起来。认识到国家需要为物理科学研究生提供高质量、消息灵通的职业指导，首席研究员将组织一系列研讨会，培训教师如何最好地提供这种指导。两年一次的COMPASS（科学学生职业发展的职业和职业指导）研讨会将向教师介绍职业规划和指导资源，并为他们在各自的机构实施有效的研究生指导做好准备。希望这种强有力的指导将帮助科学研究生做好充分准备，将他们的技术知识转化为stem相关职业所需的全部技能。全国都认识到这种努力的必要性，在美国国家科学基金会的支持下，我们希望尽可能多的机构的教师都能参加这一系列的研讨会。二世。在过去的几十年里，凝聚态物理的深入研究集中在具有强电子相关性的材料上。包含f壳层元素的近藤晶格材料是一类具有丰富历史的强相关电子系统，关键的挑战是理解局部f矩的磁有序及其与传导电子的杂化之间的相互作用。在这项研究中，我们重点阐明了一种特殊类型的近道晶格问题的解决方案，该问题的离子，如镨3+，含有偶数个f电子，基态是非克莱默斯重态。最近发现的一类此类材料，特别是PrV2Al20和PrTi2Al20，表现出非常丰富的行为，包括不寻常的四极磁性，非费米液态金属相和非常规的超导性。智力优势：迄今为止，大多数关于非克雷默斯f离子的理论研究都集中在四极有序的性质上，或者集中在多通道近藤效应的有效平均场描述上，这种效应发生在非克雷默斯双重态被传导电子屏蔽时。这一建议的主要智力价值在于以一种整体的方式将这两个方面结合起来，旨在回答磁多极秩序如何被近藤杂化抑制的问题；量子临界点的本质是什么，观察到的非费米液体行为是如何产生的；以及超导的本质是什么。重要的是，所提出的研究将超越多极序的平均场描述，包括量子涨落的影响，并将采用先进的分析和数值技术来阐明近藤杂交的影响，而不是以前所做的。如果成功的话，这项研究有可能显著提高该领域的技术水平，并提高我们对这些材料中强电子相互作用基本方面的理解。更广泛的影响:认识到国家对高质量、信息丰富的物理科学研究生职业指导的需求，我们建议组织一系列两年一次的COMPASS（理科生职业发展的职业和职业指导）研讨会，向教师介绍职业规划和指导资源，并向他们提供如何使用这些资源的描述。并准备他们制定具体的行动计划，在他们的机构实施研究生辅导。希望这种强有力的指导将帮助科学研究生做好充分准备，将他们的技术知识转化为stem相关职业所需的全部技能。全国都认识到这种努力的必要性，在美国国家科学基金会的支持下，我们希望尽可能多的机构的教师都能参加这一系列的研讨会。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

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• 发表时间: 2020-10
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• 影响因子: 8.6
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