Visualizing quantum Hall ferromagnets, their 1D topological edge modes and their interplay with superconductivity

可视化量子霍尔铁磁体、其一维拓扑边缘模式及其与超导性的相互作用

• 批准号: 1904442
• 负责人: Ali Yazdani
• 金额: $ 54万
• 依托单位: Princeton 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: 2019-07-15 至 2023-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1904442&HistoricalAwards=false
• 关键词: Visualizing; quantum; Hall; ferromagnets; their

Non-technical AbstractResearch on topological phases has connection to both concepts in quantum field theory and proposed approaches for creation of fault tolerant quantum computers. The idea that low energy, emergent quasiparticles in condensed matter systems can provide a laboratory to test field theory concepts follows the long tradition of generalizing concepts in physics across energy and length scales. Equally important to the study of topological materials, topological phases and associated emergent quasiparticles may well provide fundamental new approaches to electronics. For example, valley degree of freedom for electronic wavefunction in solids, a property examined here, is a feature that has been proposed to create new types of electronic devices. The graduate and undergraduate students trained on this project are learning state-of-the-art scanning probe microscopy, cryogenics, and materials physics experimental techniques that are of strong interest to both industry and academia. Lab research is being moved into the classroom with the development of a Princeton freshman seminar course introducing students to some basics of quantum mechanics, quantum computing, and exposing them to 'tabletop' discoveries in quantum condensed matter physics such as superconductivity, superfluidity, laser cooling and Bose condensation. The course is designed to introduce quantum phenomena to those with minimal training, with only high school courses in science and math. This approach will allow students from various academic backgrounds and interests to be exposed to the excitement of condensed matter physics and quantum phenomena early in their career.Technical AbstractThis project is focused on the study of electronic phases in which interaction between electrons and topology of their wavefunctions must be treated on equal footing. These are quantum Hall ferromagnetic phases in which electrons' valley degree of freedom makes the topological quantum Hall states also display broken symmetry driven by the exchange interaction between electrons. To accomplish its goals, the program brings the power of high energy and spatial resolution spectroscopic mapping with a scanning tunneling microscope (STM) to not only visualize valley quantum Hall ferromagnets in real space, but also to probe their topological boundary modes and to tune their properties by changing their carrier density, or using strain, and proximity with superconductors and magnets. A new class of interacting 1D Luttinger liquids that form at the topological boundary between different quantum Hall valley phases is examined during this program. In addition, the program explores the physics of interactions at low carrier concentrations to drive stripe, bubble, or fractional quantum Hall phases in an electronic system (Bi and other surface states) accessible to STM, and visualize these phases for the first time. The interplay between quantum Hall valley-polarized phases with superconductivity in special hybrid structures are also studied. These efforts will explore ways in which Majoranas' "lattices" and topological superconductivity may emerge when a vortex lattice from a conventional superconductor is coupled with a two-dimensional (2D) electron gas with strong spin-orbit coupling in the presence of a quantized Landau level (LL). A number of different materials will be explored to extend our ability to visualize Landau wavefunction to other 2D systems. The program will bring together a wide range of experiments, novel creation of materials and thin film structures to realize topological electronic phases and associated novel phenomena that can be directly studied with high spatial and energy resolution using the STM. The research is made possible by high-resolution STM instrumentation that have been designed and constructed by the principal investigator and his research team.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.

拓扑相位的研究既与量子场论中的概念有关，也与容错量子计算机的创建方法有关。凝聚态系统中的低能量、涌现的准粒子可以提供一个实验室来测试场论概念，这一想法遵循了跨越能量和长度尺度的物理学概念推广的悠久传统。对拓扑材料的研究同样重要的是，拓扑相和相关的涌现准粒子很可能为电子学提供基本的新方法。例如，固体中电子波函数的谷自由度，这里研究的一个属性，是一个被提出用于创建新型电子设备的特征。本项目培养的研究生和本科生将学习到业界和学术界都非常感兴趣的最先进的扫描探针显微镜、低温学和材料物理实验技术。随着普林斯顿大学新生研讨会课程的发展，实验室研究正在进入课堂，向学生介绍量子力学、量子计算的一些基础知识，并让他们接触量子凝聚态物理的“桌面”发现，如超导、超流体、激光冷却和玻色凝聚。这门课程旨在向那些只接受过高中科学和数学课程的人介绍量子现象。这种方法将允许来自不同学术背景和兴趣的学生在他们的职业生涯早期接触到凝聚态物理和量子现象的兴奋。技术摘要：本课题主要研究电子相，在电子相中，电子之间的相互作用及其波函数的拓扑结构必须同等对待。这些是量子霍尔铁磁相，其中电子的谷自由度使得拓扑量子霍尔态也显示出由电子之间的交换相互作用驱动的破缺对称性。为了实现其目标，该计划利用扫描隧道显微镜（STM）的高能量和空间分辨率光谱映射的能力，不仅可以在实际空间中可视化山谷量子霍尔铁磁体，还可以探测它们的拓扑边界模式，并通过改变载流子密度或使用应变以及与超导体和磁体的接近度来调整它们的特性。在这个程序中，研究了在不同量子霍尔谷相之间的拓扑边界上形成的一类新的相互作用1D卢廷格液体。此外，该项目还探索了低载流子浓度下的相互作用物理，以驱动STM可访问的电子系统（Bi和其他表面态）中的条纹、气泡或分数量子霍尔相，并首次将这些相可视化。研究了特殊杂化结构中具有超导性的量子霍尔谷极化相之间的相互作用。这些努力将探索当来自传统超导体的涡流晶格与具有强自旋轨道耦合的二维（2D）电子气体在量子化朗道能级（LL）存在下耦合时，Majoranas的“晶格”和拓扑超导性可能出现的方式。将探索许多不同的材料，以扩展我们将朗道波函数可视化到其他二维系统的能力。该计划将汇集广泛的实验，材料和薄膜结构的新创造，以实现拓扑电子相和相关的新现象，可以使用STM以高空间和能量分辨率直接研究。这项研究是由首席研究员和他的研究团队设计和建造的高分辨率STM仪器实现的。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

Insulators at fractional fillings in twisted bilayer graphene partially aligned to hexagonal boron nitride

• DOI: 10.1063/10.0019422
• 发表时间: 2023-03
• 期刊: Low Temperature Physics
• 影响因子: 0.8
• 作者: Dillon Wong;Kevin P. Nuckolls;Myungchul Oh;Ryan L. Lee;Kenji Watanabe;T. Taniguchi;A. Yazdani

Evidence for unconventional superconductivity in twisted bilayer graphene

• DOI: 10.1038/s41586-021-04121-x
• 发表时间: 2021-10-20
• 期刊: NATURE
• 影响因子: 64.8
• 作者: Oh, Myungchul;Nuckolls, Kevin P.;Yazdani, Ali
• 通讯作者: Yazdani, Ali

Evidence for a monolayer excitonic insulator

• DOI: 10.1038/s41567-021-01422-w
• 发表时间: 2021-12-23
• 期刊: NATURE PHYSICS
• 影响因子: 19.6
• 作者: Jia, Yanyu;Wang, Pengjie;Wu, Sanfeng
• 通讯作者: Wu, Sanfeng

High mobility in a van der Waals layered antiferromagnetic metal

• DOI: 10.1126/sciadv.aay6407
• 发表时间: 2020-02-01
• 期刊: SCIENCE ADVANCES
• 影响因子: 13.6
• 作者: Lei, Shiming;Lin, Jingjing;Schoop, Leslie M.
• 通讯作者: Schoop, Leslie M.

A modular ultra-high vacuum millikelvin scanning tunneling microscope

• DOI: 10.1063/1.5132872
• 发表时间: 2020-02-01
• 期刊: REVIEW OF SCIENTIFIC INSTRUMENTS
• 影响因子: 1.6
• 作者: Wong, Dillon;Jeon, Sangjun;Yazdani, Ali
• 通讯作者: Yazdani, Ali