CAREER: Revealing the Dynamics of Charge Carriers in Strongly Correlated Materials with Scanning Tunneling Potentiometry

职业：通过扫描隧道电位法揭示强相关材料中电荷载流子的动力学

• 批准号: 2239478
• 负责人: Victor Brar
• 金额: $ 89.51万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-06-01 至 2028-05-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2239478&HistoricalAwards=false
• 关键词: CAREER; Revealing; Dynamics; Charge; Carriers

Non-technical abstract: The way in which electrons and heat move through a material is often assumed to resemble billiard balls or diffusive spreading, but in many materials this is not the case and the movement is unknown. This project aims to develop new microscopy techniques that can be used to directly visualize the flow of electrons and heat in a material at the microscopic level. Understanding that motion allows materials to be produced that have less resistance, better heat conductivity, and that can model fluid and air flows in ways that are less costly than current methods. A significant aspect of this project is to develop touch-based learning tools for understanding the physics of materials, where students use tactile models and haptic-feedback systems to ‘feel’ the crystal lattice of a material in the same way an electron or molecule would. These lessons are being developed for advanced undergraduate labs and for K-12 outreach programs, with an aim of explaining the properties of materials in an intuitive and memorable way. A travelling class is also being developed for older adults and differently sighted individuals, so that they can learn about materials in an engaging tactile manner; and a class in being developed for Grandparents University at the University of Wisconsin, where older adults and their grandchildren learn about scientific concepts together.Technical abstract: This project aims to advance and utilize two scanned probe techniques – scanning tunneling potentiometry (STP) and scanning tunneling superconducting thermometry (STST) – to separately image the nanoscale flow of charge and heat in materials, such as graphene, with hydrodynamic and quantum hall phases. Hydrodynamic material systems exhibit novel thermoelectric properties that violate the Wiedemann-Franz law, and have been predicted to display vortical or even turbulent electron and heat flow. Combined STP and STST measurements are used in this project to determine the degree to which heat and charge flow becomes uncorrelated in such systems, and this project also utilizes engineered potential barriers that affect heat and charge flow differently, with an aim of further decoupling the two. Moreover, by probing how heat is dissipated in viscous electronic phases, this project explores the mechanisms that limit the conductivity of such phases and provides data that allows the complete problem of thermoelectric flow to be solved self-consistently in hydrodynamic materials. STP measurements of charge motion in magnetic fields, meanwhile, explore how weakly bound states and snake states can perturb the values of quantum hall conductance plateaus and precipitate the formation of vorticies of circularly flowing charge as the viscosity of the system is increased. These measurements also test predictions that electron viscosity itself should become quantized in quantum hall systems. This project has broad implications for creating improved thermoelectric devices from hydrodynamic materials, and for understanding the effect of hydrodynamics on other material systems.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：通常假定电子和热量通过材料移动的方式类似于台球或不同的扩散，但是在许多材料中，这种情况并非如此，并且运动尚不清楚。该项目旨在开发新的显微镜技术，这些技术可用于直接可视化微观水平的材料中的电子和热量。了解该运动允许产生材料，具有较小的电阻，更好的热导率，并且可以以比当前方法较差的方式对流体和空气流进行建模。该项目的一个重要方面是开发基于触摸的学习工具，以理解材料的物理学，在该工具中，学生使用触觉模型和触觉反馈系统来“感受”材料的晶格，就像电子或分子一样。这些课程是针对高级本科实验室和K-12外展计划开发的，还为老年人和不同视力的人开发了一个旅行班，以便他们可以以引人入胜的触觉学习材料； and a class in being developed for Grandparents University at the University of Wisconsin, where older adults and their grandchildren learn about scientific concepts together.Technical abstract: This project aims to advance and utilize two scanned probe techniques – scanning tunneling potentiometry (STP) and scanning tunneling superconducting thermometry (STST) – to separate image the nanoscale flow of charge and heat in materials, such as石墨烯，具有流体动力和量子大厅相。流体动力材料系统暴露了违反Wiedemann-Franz定律的新型热电特性，并被预测显示出涡流甚至湍流的电子和热流。该项目中使用了组合的STP和STST测量值，以确定在此类系统中热和电荷流不相关的程度，并且该项目还利用了不同影响热和电荷流的工程潜在障碍，以进一步将两者解耦。此外，通过探测如何在粘性电子相中耗散热量，该项目探讨了限制此类相的电导率的机制，并提供了允许在流体动力材料中自一自求解的热电流完全问题的数据。磁场中电荷运动的STP测量值是指较弱的状态和蛇状态如何扰动量子霍尔电导量的值，并随着系统粘度的增加而形成循环流动电荷的涡流的形成。这些测量还测试了电子粘度本身应在量子厅系统中进行量化的预测。该项目对从流体动力材料创建改进的热电设备以及理解流体动力学对其他材料系统的影响具有广泛的含义。该奖项反映了NSF的法定任务，并通过使用基金会的智力优点和更广泛的影响来评估NSF的法定任务。