Time Resolved Probing of Unconventional Orders in Novel Kagome Metals

新型 Kagome 金属中非常规有序的时间分辨探测

• 批准号: 2226519
• 负责人: Nuh Gedik
• 金额: $ 72万
• 依托单位: Massachusetts Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-02-15 至 2027-01-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2226519&HistoricalAwards=false
• 关键词: Time; Resolved; Probing; Unconventional; Orders

Nontechnical Abstract:Despite tremendous advances in the recent decades, conventional electronics based on silicon will soon hit a limit. One way to circumvent this is to use novel materials with unconventional properties. In this respect, there has been a tremendous interest in a new class of metals in which the atoms are arranged in periodic patterns of corner sharing triangles known as the Kagome lattice. The electrons in these systems behave in a highly unusual manner displaying strong repulsion, geometric frustration and topological properties. When these materials are cooled, first they go into a state in which the electron density is periodically modulated (charge density wave) and upon further cooling, they become superconductors. A key challenge is to understand the mechanism of these phases and the relationship between the two. The goal of this project is to use different types of optical and electron based spectroscopies to investigate the charge density wave state of these novel Kagome metals. A central part of this project is the training of next generation of students both in advanced spectroscopies as well as in novel quantum materials. This program will also contribute to K-12 science education and improve the physics education at the freshman level.Technical Abstract:Recently, a new class of superconducting transition-metal Kagome compounds were discovered which display a complex interplay between multiple order parameters. Above the superconducting phase transition, these materials host a charge density wave order and a putative short-ranged chiral flux phase in which both inversion and time-reversal symmetry are broken. This project aims to use an array of ultrafast optical and electron probes to investigate the highly unconventional phase diagram of these systems. With static- and time-resolved Kerr rotation microscopy, the time-reversal symmetry-breaking suggested by recent muon spin relaxation measurements is studied at a length scale inaccessible to other probes. By aligning domains of opposite chirality with circularly polarized light, the chiral charge density wave order proposed by scanning tunneling measurements is investigated with second harmonic generation. Finally, the competition or cooperation between different charge density waves will be probed by a combination of ultrafast electron diffraction and time- and angle-resolved photoemission spectroscopy which will directly yield dynamics of electronic and lattice structure. These experiments will provide a comprehensive picture of the microscopic interactions in these materials and will shed light on to the unconventional orders.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.

非技术摘要：尽管在最近几十年中取得了巨大进步，但基于硅的传统电子产品将很快达到极限。绕过这一点的一种方法是使用具有非常规性能的新型材料。在这方面，对新的金属产生了极大的兴趣，在新的金属中，原子以周期性的方式排列，分别共享称为kagome晶格的三角形。这些系统中的电子以高度不寻常的方式表现出强烈的排斥，几何挫败感和拓扑特性。当这些材料冷却时，首先它们进入一个周期性调节电子密度的状态（电荷密度波），然后进一步冷却，它们成为超导体。一个关键的挑战是了解这些阶段的机制以及两者之间的关系。该项目的目的是使用不同类型的基于光学和电子的光谱镜研究这些新型Kagome金属的电荷密度波状态。该项目的主要部分是对高级光谱和新型量子材料中的下一代学生的培训。该计划还将为K-12科学教育做出贡献，并在新生级别改善物理教育。技术摘要：最近发现了一类新的超导过渡金属kagome化合物，这些化合物在多订单参数之间显示了复杂的相互作用。在超导相变的上方，这些材料具有电荷密度波顺序和推定的短距性手性通量相，其中反转和时间反向对称性都破裂。该项目旨在使用一系列超快光学和电子探针来研究这些系统的高度非常规相图。使用静态和时间分辨的Kerr旋转显微镜，对最近的MUON自旋弛豫测量测量所暗示的时间交流对称性破坏了其他探针无法访问的长度。通过将相反手性的域与圆极化的光对齐结构域，通过第二次谐波产生研究了通过扫描隧道测量提出的手性电荷密度波顺序。最后，通过超快电子衍射以及时间和角度分辨光发射光谱的组合，将探测不同电荷密度波之间的竞争或合作，该光谱将直接产生电子和晶格结构的动力学。这些实验将为这些材料中的微观相互作用提供全面的了解，并阐明了非常规的命令。该奖项反映了NSF的法定任务，并被认为是通过基金会的智力优点和更广泛影响的审查标准通过评估来获得支持的。