The Nanoscale Effects of Intrinsic and Externally-Applied Strain on Charge Density Wave States

内在和外部施加的应变对电荷密度波态的纳米级影响

• 批准号: 1904918
• 负责人: Michael Boyer
• 金额: $ 42.71万
• 依托单位: Clark University
• 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 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1904918&HistoricalAwards=false
• 关键词: Nanoscale; Effects; Intrinsic; Externally; Applied

Non-technical abstract:Charge density wave states occur in numerous materials where, below a certain "transition" temperature, there is a periodic lattice distortion, and a periodic variation in electron density is established across the material. The electronic properties of the material are altered from the material's original, undistorted state. Charge density wave-hosting materials have been targeted for potential use in electronic devices (such as switches, ion field-effect transistors, and logic circuits). However, there is currently an incomplete understanding as to 1) the origin of charge density wave states, as well as 2) how these states coexist/interact with other technologically-important material properties such as superconductivity or magnetism. Strain engineering is an emerging field in which the application of strain to materials is used to manipulate their optical, electronic, and structural properties. In this project, controlled strain is applied to materials hosting charge density wave states, so as to compress, stretch, or shear the materials, leading to changes in their properties. Scanning tunneling microscopy, a technique which can detail electronic and structural changes in a material on the atomic scale, is used to, simultaneously, detail the evolution of charge density wave states under, both, varying strain and temperature conditions. An overarching goal of the project is to develop a fundamental understanding of the physics governing these compounds. An understanding of how to effectively manipulate their properties in a controlled fashion, is essential for optimizing their performance in devices. This project enhances the education of undergraduate- and graduate-student participants who are developing essential skills with applications in research, industry, and beyond. In addition, mini-classes using experimental techniques such as scanning tunneling microscopy, atomic force microscopy, and scanning electron microscopy, are being developed and incorporated into established, STEM-focused local outreach programs. In particular, these classes will expose precollege students to cutting-edge experimental techniques, providing a unique experience and opportunity for these students to become interested and engaged in STEM fieldsTechnical abstract:Charge density wave (CDW) states are prevalent in condensed matter systems where they are often found to coexist with other orders. The nature of the interplay of CDW states with quantum orders, such as superconductivity and magnetism, particularly on the nanoscale, is complex and not well-understood. In addition, CDW states can have differing and not always well-established origins, further complicating this understanding. Studies of CDW-hosting compounds demonstrate that strain can alter an array of CDW properties, including changing the transition temperature, altering electronic and structural periodicities of the CDW state, and changing the associated electronic band gap. The overarching goals of this NSF project are to understand 1) how strain drives these CDW changes on the atomic-scale, and 2) how to manipulate these changes in a controlled fashion using externally-applied strain. To do this, temperature-dependent scanning tunneling microscopy is used to probe the nanoscale structural and electronic properties of charge density wave states, their formation, their manipulation, and their interplay with coexisting quantum orders, under quantifiable and varied strained conditions. In order to study fundamental differences strain has on CDW states arising from differing origins (for example, Fermi surface nesting versus momentum-dependent electron-phonon coupling), compounds from three well-known, distinct, CDW-hosting families are studied: the blue bronzes, transition metal dichalcogenides, and the rare-earth tellurides. This project supports the research education of graduate and undergraduate students through their participation in all aspects of the project. Furthermore, in an effort to extend science education to precollege students who are historically underrepresented in the sciences (precollege girls and students from the many lower-income households in the local community), the principal investigator is developing mini-classes on "probing material properties" which utilizes Clark facilities to expose area students to the basics of materials research. These classes will be held in connection with established, STEM-focused outreach collaborations involving local area middle and high school students.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：电荷密度波状态出现在许多材料中，在许多材料中，在某个“过渡”温度以下，存在周期性的晶格失真，并且在整个材料之间建立了电子密度的周期性变化。材料的电子特性是根据材料原始的未发生的状态改变的。电荷密度波托材料已被针对电子设备（例如开关，离子场效应晶体管和逻辑电路）的潜在用途。但是，目前对1）电荷密度波状态的起源以及2）这些状态如何与其他技术重要的物质特性（例如超导性或磁性）并存/相互作用。应变工程是一个新兴领域，在该领域中，应将应变应用于材料来操纵其光学，电子和结构特性。在该项目中，受控应变被应用于托管电荷密度波状态的材料，以压缩，拉伸或剪切材料，从而导致其性质变化。扫描隧道显微镜是一种可以详细说明原子量表上电子和结构变化的技术，用于同时详细介绍电荷密度波状态的演变，无论应变和温度条件都不同。该项目的总体目标是对管理这些化合物的物理学有基本的理解。了解如何以受控方式有效地操纵其属性，这对于优化其在设备中的性能至关重要。该项目增强了在研究，行业及其他领域的应用中开发基本技能的本科和研究生的教育。此外，开发并纳入了以扫描隧道显微镜，原子力显微镜和扫描电子显微镜之类的实验技术的迷你级，并正在开发中，并将其纳入建立的，注重茎的局部外展计划中。特别是，这些课程将使预科学生接触到尖端的实验技术，为这些学生提供兴趣和参与STEM现场技术摘要的独特经验和机会：电荷密度波（CDW）状态在冷凝的物质系统中普遍存在，在这些系统中，他们经常被发现与其他订单共存。 CDW状态与量子阶的相互作用的性质，例如超导性和磁性，尤其是在纳米级上，是复杂的，并且不被善待。此外，CDW状态可能具有不同的起源，并且并非总是建立的，这进一步使这种理解变得复杂。 CDW托管化合物的研究表明，应变可以改变CDW特性，包括改变过渡温度，改变CDW状态的电子和结构周期性，并改变相关的电子带隙。该NSF项目的总体目标是了解1）应变如何驱动原子尺度上的这些CDW变化，以及2）如何使用外部应用菌株以受控的方式操纵这些变化。为此，使用依赖温度的扫描隧道显微镜来探测电荷密度波状态的纳米级结构和电子性能，它们的形成，操作以及与共存的量子阶的相互作用，在可量化的量子下，在可量化和变化的条件下。为了研究菌株对不同起源产生的CDW状态的基本差异（例如，费米表面嵌套与动量依赖性电子 - phonon耦合），研究了三个众所周知的，独特的，CDW的辅助家族的化合物：蓝铜，蓝铜，蓝铜，过渡金属dichalcogenides和稀有的细胞。该项目通过参与该项目的各个方面来支持研究生和本科生的研究教育。此外，为了将科学教育扩展到在科学中的人数不足的预科学生（从当地社区中许多低收入家庭的预科女孩和学生）中的人数不足的学生，首席研究人员正在开发有关“企业材料”的迷你阶级，这些材料利用Clark设施来使学生区域学生将基础学生探讨材料研究的基础研究。这些班级将与涉及当地中学和高中生的既定，注重STEM的外展合作有关。该奖项反映了NSF的法定任务，并使用基金会的知识分子优点和更广泛的影响审查标准，被认为值得通过评估。

项目成果

Interplay of charge density wave states and strain at the surface of CeTe2

• DOI: 10.1103/physrevb.101.245423
• 发表时间: 2019-11
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: Bishnu Sharma;M. Singh;Burhan Ahmed;Boning Yu;P. Walmsley;I. Fisher;M. Boyer