Disorder and the Emergence of Inhomogeneous Phases in Strongly Correlated Electron Systems

强相关电子系统中的无序和非均匀相的出现

• 批准号: 1849751
• 负责人: Peter Hirschfeld
• 金额: $ 35.55万
• 依托单位: University of Florida
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-08-01 至 2023-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1849751&HistoricalAwards=false
• 关键词: Disorder; Emergence; Inhomogeneous; Phases; Strongly

NONTECHNICAL SUMMARYThis award supports research and education designed to advance understanding of materials containing itinerant electrons that interact strongly with each other, giving rise to new states of electronic matter with novel properties. The PI will use model calculations for electrons in materials classes known as cuprates and iron-based superconductors, as well as others, to study several challenging problems directed towards a broader understanding of how these materials work. He will also work with a local science museum to prepare exhibits on superconductivity and magnetism for the general public.Superconductivity is one type of quantum state of many electrons in a metal that is characterized by the loss of all electrical resistance and consequently of all dissipation of energy. The PI will explore the interplay between the fundamental physics of superconductors and other phases of matter, including magnetic ones, which tend to form when superconductivity is suppressed. In addition, he will explore the effect of impurities and other defects that are always present when crystals or films are grown, on the interplay between these phases. Thus, the PI will explore models of the effect of impurities and other real-life defects on the properties of these superconducting materials. The PI will focus especially on the theory of how to interpret results from an experimental technique called scanning tunneling spectroscopy. In this method, atomic-resolution images of the quantum states of a material can be collected by applying a voltage to a tiny sharp metal tip as it is scanned over the material's surface. Information obtained from theoretical calculations and the analysis of data from these experiments may provide key insights into the interplay of superconductivity and other states including magnetism and a novel state of electrons that is a quantum mechanical analog of states that occur in liquid crystals and make liquid crystal displays possible, and their interaction with impurities in the material.One consequence of these investigations may be a deeper insight into the nature of high temperature superconductivity and how it can be further optimized to have enormous technological implications. Understanding the properties of these quantum materials and the influence of disorder may also lead to novel properties that can be utilized in new devices and technologies, obtaining unusual sensitivity operating near transitions among competing phases that occur in highly correlated metals.TECHNICAL SUMMARYThis award supports theoretical research and education to address long-standing fundamental problems involving the interplay of quenched disorder and various types of competing emergent order in correlated electron systems. The materials to be investigated include cuprate and iron-based superconductors, as well other quantum materials displaying competing orders. The PI will investigate properties of electronic systems through a careful analysis of the behavior of simplified models of interacting electrons on the lattice, informed in some cases by density functional theory-based electronic structure calculations with appropriate inclusion of correlations. There are three main projects:1. Interplay of nematicity, superconductivity, and disorder. The PI and his group will study the influence of impurities on electronic nematic instabilities in Fe-based superconducting systems and their interplay with superconductivity. Normally it is expected that superconductivity and nematicity compete with one another, as seen clearly in the Barium122 system. This competition may be responsible for the striking enhancement of the transition temperature with electron irradiation in iron selenide, but recent experiments on iron materials that include both selenium and sulfur in proportion have indicated that in some chalcogenide systems nematicity and superconductivity cooperate with each other, and this unusual situation may be responsible for the enhancement of the transition temperature with disorder as observed in iron selenide. A wide range of behavior is possible, and the PI will investigate the phase diagram of simple models that allow for both competition and cooperation, as well as how these phases evolve with disorder. The PI aims to address the basic question: What in a material system influences whether or not nematicity and superconductivity cooperate or compete, and how can disorder affect this balance?2. Effects of disorder on overdoped cuprates. The PI will perform a series of investigations on the cuprate materials that can be doped well past optimal doping, to show the unexpected effects of scattering from out-of-plane dopants, and test the hypothesis that the overdoped cuprate superconducting state can be well described by the Landau-BCS paradigm. This notion was challenged by recent superfluid density and optical conductivity experiments on lanthanum strontium copper oxide (LSCO) films. The PI and his group will calculate several measurable quantities in the superconducting state of LSCO and related bismuth, thallium and other cuprate compounds using the so-called dirty d-wave theory. One goal will be to examine the effect of disorder as a possible explanation for the disparate transition temperatures in these systems. The PI's work will be complemented by studies of the doping dependence of the intrinsic pairing interaction in Hubbard-type models to see if a consistent picture can be developed where pseudogap physics is apparently absent. Finally, ab initio calculations of out-of-plane dopant impurity potentials will be performed to allow for possible microscopic justification of the established phenomenology. 3. STM of charge and pair density waves. Much of the physical information available on competing order and inhomogeneity arises from scanning tunneling microscopy and spectroscopy on high quality surfaces; yet the theory to interpret such data is available only in very primitive form. The PI will use microscopic Wannier functions from ab initio calculations to construct local Green's functions in both superconducting and metallic states to compare with experiments on charge and density waves, above the sample surface where measurements are actually performed. This technique will be tested on longstanding problems in cuprate and iron-based superconductors, and then extended to study modern issues of competing order in a variety of correlated systems. In particular, the PI and his group will compare microscopic theories of pair density waves in cuprates with STM data.Understanding the properties of correlated electron systems and the influence of disorder may lead to novel materials properties that can be utilized in new devices and technologies, obtaining unusual sensitivity by operating near transitions between competing phases that occur in highly correlated electron systems.This award also supports outreach activities including: designing a new exhibit on electrical conduction and superconductivity for the recently opened Cade Museum for Innovation, organizing U. Florida Activities in support of United Nations Women and Girls in Science Day, and developing and delivering public lectures. Software developed for the calculation of spin fluctuation pairing, and a database for Wannier functions in unconventional superconductors, will be made available through the PI's website and GitHub.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.

该奖项支持旨在促进对含有流动电子的材料的理解的研究和教育，这些流动电子彼此强烈相互作用，产生具有新特性的电子物质的新状态。PI将使用模型计算铜酸盐和铁基超导体等材料中的电子，以及其他材料，研究几个具有挑战性的问题，以更广泛地了解这些材料是如何工作的。他还将与当地一家科学博物馆合作，为公众准备超导和磁力展览。超导是金属中许多电子的一种量子态，其特征是失去所有电阻，从而导致所有能量的耗散。PI将探索超导体的基本物理与物质的其他相之间的相互作用，包括磁性相，当超导性被抑制时，磁性相往往会形成。此外，他将探索在晶体或薄膜生长时，杂质和其他缺陷对这些相之间相互作用的影响。因此，PI将探索杂质和其他实际缺陷对这些超导材料性能影响的模型。PI将特别关注如何解释一种叫做扫描隧道光谱的实验技术的结果的理论。在这种方法中，材料的量子态的原子分辨率图像可以通过在扫描材料表面时对微小的尖锐金属尖端施加电压来收集。从这些实验的理论计算和数据分析中获得的信息可能为超导和其他状态的相互作用提供关键的见解，包括磁性和一种新的电子状态，这是液晶中发生的状态的量子力学模拟，使液晶显示成为可能，以及它们与材料中杂质的相互作用。这些研究的一个结果可能是更深入地了解高温超导的本质，以及如何进一步优化它以产生巨大的技术影响。了解这些量子材料的特性和无序的影响也可能导致新的特性，这些特性可以用于新的设备和技术，在高度相关的金属中发生的竞争相之间的过渡附近获得不同寻常的灵敏度。该奖项支持理论研究和教育，以解决长期存在的基本问题，涉及相关电子系统中淬火无序和各种类型的竞争紧急秩序的相互作用。要研究的材料包括铜基和铁基超导体，以及其他显示竞争顺序的量子材料。PI将通过仔细分析晶格上相互作用电子的简化模型的行为来研究电子系统的特性，在某些情况下，通过基于密度泛函理论的电子结构计算，适当地包含相关性。主要有三个项目：1。向列性、超导性和无序性的相互作用。PI和他的团队将研究杂质对铁基超导系统中电子向列不稳定性的影响及其与超导性的相互作用。通常人们认为超导性和向列性是相互竞争的，正如在钡122系统中所看到的那样。这种竞争可能是硒化铁在电子辐照下转变温度显著提高的原因，但最近对含硒和含硫的铁材料的实验表明，在某些硫系中，向列性和超导性是相互合作的，这种不寻常的情况可能是硒化铁中观察到的转变温度无序提高的原因。广泛的行为是可能的，PI将研究允许竞争和合作的简单模型的阶段图，以及这些阶段如何随无序而演变。PI旨在解决基本问题：在材料系统中是什么影响向列性和超导性是合作还是竞争，以及无序如何影响这种平衡？无序对过量掺杂铜酸盐的影响。PI将对超过最佳掺杂的铜材料进行一系列的研究，以显示面外掺杂的散射的意想不到的影响，并验证过掺杂铜超导态可以用Landau-BCS范式很好地描述的假设。最近在镧锶铜氧化物（LSCO）薄膜上进行的超流体密度和光电导率实验对这一概念提出了挑战。PI和他的团队将使用所谓的脏d波理论计算LSCO和相关铋、铊和其他铜化合物的超导状态下的几个可测量量。一个目标将是检验无序的影响，作为这些系统中不同转变温度的可能解释。PI的工作将通过对哈伯德模型中内在配对相互作用的掺杂依赖性的研究来补充，以查看是否可以在假间隙物理明显缺失的情况下发展出一致的图像。最后，从头开始计算面外掺杂杂质势，以允许建立现象学的可能的微观证明。3. 电荷和对密度波的STM。许多关于竞争秩序和非均匀性的物理信息来自高质量表面的扫描隧道显微镜和光谱学；然而，解释这些数据的理论还只是非常原始的形式。PI将使用从头计算的微观万尼尔函数来构建超导和金属状态下的局部格林函数，以与实际进行测量的样品表面以上的电荷波和密度波实验进行比较。这项技术将在铜基和铁基超导体中长期存在的问题上进行测试，然后扩展到研究各种相关系统中竞争秩序的现代问题。特别是，PI和他的团队将比较铜酸盐中对密度波的微观理论与STM数据。了解相关电子系统的特性和无序的影响可能会导致新的材料特性，这些特性可以用于新的设备和技术，通过在高度相关的电子系统中发生的竞争相之间的近跃迁操作获得不同寻常的灵敏度。该奖项还支持外展活动，包括：为最近开放的凯德创新博物馆设计一个关于导电和超导的新展览，组织佛罗里达大学活动以支持联合国妇女和女童参与科学日，以及编写和发表公开讲座。为计算自旋涨落配对而开发的软件，以及非常规超导体中的万尼尔函数数据库，将通过PI的网站和GitHub提供。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

Superconducting gap symmetry from Bogoliubov quasiparticle interference analysis on Sr2RuO4

• DOI: 10.1103/physrevb.107.144505
• 发表时间: 2021-09
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: S. Bhattacharyya;A. Kreisel;X. Kong;T. Berlijn;A. T. Rømer;B. M. Andersen;P. Hirschfeld

Magnetic anisotropy from linear defect structures in correlated electron systems

• DOI: 10.1103/physrevb.103.245132
• 发表时间: 2020-12
• 期刊: arXiv: Strongly Correlated Electrons
• 作者: Mainak Pal;Laetitia P. Bettmann;A. Kreisel;P. Hirschfeld

Simulating superconducting properties of overdoped cuprates: The role of inhomogeneity

模拟过掺杂铜酸盐的超导特性：不均匀性的作用

• DOI: 10.1103/physrevb.107.144501
• 发表时间: 2023
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: Pal, Mainak;Kreisel, Andreas;Atkinson, W. A.;Hirschfeld, P. J.
• 通讯作者: Hirschfeld, P. J.

Comment on “Anisotropic Scattering Caused by Apical Oxygen Vacancies in Thin Films of Overdoped High-Temperature Cuprate Superconductors”

对“过掺杂高温铜酸盐超导体薄膜中顶端氧空位引起的各向异性散射”的评论

• DOI: 10.1103/physrevlett.131.049701
• 发表时间: 2023
• 期刊: Physical Review Letters
• 影响因子: 8.6
• 作者: Özdemir, H. U.;Mishra, Vivek;Lee-Hone, N. R.;Kong, Xiangru;Berlijn, T.;Broun, D. M.;Hirschfeld, P. J.
• 通讯作者: Hirschfeld, P. J.

Correlations among STM observables in disordered unconventional superconductors

无序非常规超导体中 STM 可观测量之间的相关性

• DOI: 10.1103/physrevb.104.144501
• 发表时间: 2021
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: Sulangi, Miguel Antonio;Atkinson, W. A.;Hirschfeld, P. J.
• 通讯作者: Hirschfeld, P. J.