Correlated Electron Physics in Graphene and Other Novel Quantum Materials

石墨烯和其他新型量子材料中的相关电子物理

• 批准号: 1916958
• 负责人: Oskar Vafek
• 金额: $ 36万
• 依托单位: Florida State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-07-15 至 2023-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1916958&HistoricalAwards=false
• 关键词: Correlated; Electron; Physics; Graphene; Other

NONTECHNICAL SUMMARYThis award supports theoretical research and education to further our understanding of how quantum mechanics determines the state of matter of a large collection of interacting particles at the atomic level. The stages on which such dynamics plays out are real quantum materials, designed and studied within laboratories around the world using modern experimental tools. The ultimate practical goal is to use the gained understanding for designing new materials and structures with desired properties.The discovery of superconductivity --flow of electrical current without any resistance-- in a physical system composed of two sheets of graphene, each one carbon atom thin and precisely stacked on top of each other, has started a new frontier research field aligned with the above goals. In addition, many such materials combine modern notions of topology with basic concepts of solid-state physics describing the behavior of strongly interacting electron systems, an intellectual frontier still largely unexplored. The PI will study such systems using an arsenal of modern analytical and numerical tools.The projects will involve a graduate student, who will be trained in analytical and computational methods, as well as in scientific communication, via immersion in a collaborative environment working on open problems at the frontier of condensed matter physics. It will also allow the student to travel to and participate in conferences and schools, and thus engage with the broader scientific community. The skills that will be developed are essential for many successful careers in STEM fields.TECHNICAL SUMMARYThis award supports fundamental research and education aimed at understanding properties of correlated electrons in novel quantum materials. The long-term goal is to use such understanding to design new materials and structures with desired functionalities, as well as to advance theoretical tools needed for predictive analysis. The PI's research and educational activity is centered on the theoretical description of moire materials, including twisted bilayer graphene. Such systems combine modern notions of topologically nontrivial band structure and strong electron correlations. Broadly, the main thrust of the project is to understand the underlying mechanism responsible for -- and the nature of -- the correlated insulator phases observed at commensurate fillings of the narrow bands, and the nearby superconductivity observed at generally incommensurate fillings in various moire structures. The PI will study the problem using an arsenal of analytical and numerical tools, including strong-coupling expansions, variational mean-field theory, and density-matrix renormalization group. An important part of the project is the simultaneous development of simplified models capturing the physical essence of the findings obtained within more numerically involved techniques. Such models will engender deeper understanding of the physics playing out in existing materials, and will also allow greater flexibility in further qualitative predictions not easily achieved numerically.The projects will involve a graduate student, who will be trained in analytical and computational methods, as well as in scientific communication, via immersion in a collaborative environment working on open problems at the frontier of condensed matter physics. It will also allow the student to travel to and participate in conferences and schools, and thus engage with the broader scientific community. The skills that will be developed are essential for many successful careers in STEM fields.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.

非技术摘要该奖项支持理论研究和教育，以进一步了解量子力学如何在原子水平上确定大量相互作用粒子的物质状态。这种动力学发挥的舞台是真正的量子材料，是使用现代实验工具在世界各地的实验室中设计和研究的。最终的实际目标是利用所获得的理解来设计具有所需性能的新材料和结构。超导性的发现——在由两片石墨烯组成的物理系统中无任何电阻的电流流动，每个石墨烯有一个碳原子薄而精确地堆叠在一起，开启了一个与上述目标一致的新的前沿研究领域。此外，许多此类材料将现代拓扑概念与描述强相互作用电子系统行为的固态物理学基本概念相结合，这是一个很大程度上尚未探索的知识前沿。 PI 将使用现代分析和数值工具库来研究此类系统。这些项目将涉及一名研究生，他们将通过沉浸在开放式协作环境中接受分析和计算方法以及科学传播方面的培训。凝聚态物理的前沿问题。它还将允许学生前往并参加会议和学校，从而与更广泛的科学界接触。将培养的技能对于 STEM 领域的许多成功职业至关重要。技术摘要该奖项支持旨在了解新型量子材料中相关电子特性的基础研究和教育。长期目标是利用这种理解来设计具有所需功能的新材料和结构，并推进预测分析所需的理论工具。 PI 的研究和教育活动以莫尔条纹材料（包括扭曲双层石墨烯）的理论描述为中心。这种系统结合了拓扑非平凡能带结构和强电子相关性的现代概念。从广义上讲，该项目的主要目标是了解在窄带的相称填充物中观察到的相关绝缘体相位的基本机制及其性质，以及在各种莫尔结构中通常不相称的填充物中观察到的附近超导性。 PI 将使用一系列分析和数值工具来研究该问题，包括强耦合展开、变分平均场理论和密度矩阵重整化群。该项目的一个重要部分是同时开发简化模型，捕捉在更多涉及数值的技术中获得的发现的物理本质。这些模型将加深对现有材料中物理现象的理解，并且还将为进一步的定性预测提供更大的灵活性，而这在数值上是不容易实现的。这些项目将涉及一名研究生，他还将接受分析和计算方法的培训就像在科学传播中一样，通过沉浸在协作环境中，致力于解决凝聚态物理前沿的开放问题。它还将允许学生前往并参加会议和学校，从而与更广泛的科学界接触。将培养的技能对于 STEM 领域的许多成功职业至关重要。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力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

Renormalization Group Study of Hidden Symmetry in Twisted Bilayer Graphene with Coulomb Interactions

扭曲双层石墨烯中库仑相互作用隐藏对称性的重正化群研究

• DOI: 10.1103/physrevlett.125.257602
• 发表时间: 2020-12
• 期刊: Physical Review Letters
• 影响因子: 8.6
• 作者: Vafek, Oskar;Kang, Jian
• 通讯作者: Kang, Jian

Tuning electron correlation in magic-angle twisted bilayer graphene using Coulomb screening

使用库仑筛选调节魔角扭曲双层石墨烯中的电子相关性

• DOI: 10.1126/science.abb8754
• 发表时间: 2020-03-24
• 期刊: Science
• 影响因子: 56.9
• 作者: Xiaoxue Liu;Zhi Wang;K. Watanabe;T. Taniguchi;O. Vafek;J.I.A. Li
• 通讯作者: J.I.A. Li

Diagnosis of explicit symmetry breaking in the tight-binding constructions for symmetry-protected topological systems

对称保护拓扑系统紧束缚结构中显式对称破缺的诊断

• DOI: 10.1103/physrevb.102.075142
• 发表时间: 2020-02-06
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: Xiaoyu Wang;O. Vafek
• 通讯作者: O. Vafek

Phase diagram of twisted bilayer graphene at filling factor ν=±3

填充因子 ν=±3 时扭曲双层石墨烯的相图

• DOI: 10.1103/physrevb.107.075156
• 发表时间: 2023-02
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: Xie, Fang;Kang, Jian;Bernevig, B. Andrei;Vafek, Oskar;Regnault, Nicolas
• 通讯作者: Regnault, Nicolas

Trions in twisted bilayer graphene

扭曲双层石墨烯中的 Trion

• DOI: 10.1103/physrevb.105.155135
• 发表时间: 2021-12-23
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: F. Schindler;O. Vafek;B. Bernevig
• 通讯作者: B. Bernevig