Investigation of topological electronic states in atomic layered materials and heterostructures

非技术摘要：传统导体和绝缘体的区别在于它们的导电能力。拓扑绝缘子是一种将绝缘内部和导电表面结合在一起的新型材料。它们独特的电子性质可以使新一代量子技术成为可能，如量子计算机和节能电子产品。最近发现的一种材料WTe2在单层形式下表现出这样的拓扑行为。在这种二维拓扑绝缘体系统中，电流只能沿着样品的边缘流动。这个项目研究了单层WTe2的内部和边缘的电学性质，目的是了解拓扑体状态和导电边缘之间的联系，并开发通过在其他2D材料上堆积单层WTe2来操纵这些性质的新方法。研究小组还建立了一个实验工作流程，以有效筛选理论预测的候选拓扑材料，这可能会导致发现新的2D拓扑系统。该项目与教育活动相结合，旨在吸引本科生在先进的电子硬件和新仪器开发方面进行研究和培训。技术摘要：该项目旨在研究基于原子层状材料的2D系统的拓扑物理，重点是最近发现的2D拓扑绝缘体单层WTe2。该研究使用了一系列的电学表征技术来探测拓扑态的电子性质，包括通过微波阻抗显微镜的局域电导，通过静电力显微镜的化学势，以及通过量子电容测量的热力学状态密度。我们的目标是了解体电子态的性质，包括相互作用对拓扑性质的影响。该项目还探索了单层WTe2与其他2D材料的异质结构，以操纵单层WTe2的拓扑性质。该研究小组进一步开发了一种有效的实验方法来筛选预测为2D拓扑绝缘体的候选材料。该方法涉及适用于空气敏感材料研究的制造和表征技术的集成，并开发了一种最大限度地减少样品制造以提高产量的工作流程。研究生和本科生参与了实验方法的开发，提供了设备制造、仪器设计和数据分析方面的全面培训。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Non-technical Abstract:Conventional conductors and insulators are distinguished by their abilities to conduct electricity. Topological insulators are a new class of materials which combine an insulating interior with conducting surfaces. Their unique electronic properties can enable new generation of quantum technology such as quantum computers and energy efficient electronics. A recently discovered material, WTe2, exhibits such topological behavior in a single layer form. In this 2D topological insulator system, electrical current can only flow along the edges of the sample. This project investigates the electrical properties both in the interior bulk and at edges of monolayer WTe2, aiming to understand the connection between the topological bulk states and the conducting edges and to develop new methods to manipulate these properties by stacking monolayer WTe2 on other 2D materials. The research team also builds an experimental workflow to effectively screen candidate topological materials predicted by theory, which could potentially lead to discovery of new 2D topological systems. The project is integrated with education activities to attract undergraduate students to research and train them in advanced electronics hardware and development of new instrumentation.Technical Abstract:This project aims to investigate topological physics in 2D systems based on atomic layered materials, with a focus on a recently discovered 2D topological insulator, monolayer WTe2. The research employs a range of electrical characterization techniques to probe the electronic properties of the topological states, including local conductivity by microwave impedance microscopy, chemical potential by electrostatic force microscopy, and thermodynamic density of states by quantum capacitance measurement. The goal is to understand the nature of the bulk electronic states including the effect of interaction on the topological properties. The project also explores heterostructures of monolayer WTe2 with other 2D materials in order to manipulate the topological properties in monolayer WTe2. The research team further develops an effective experimental method to screen candidate materials that are predicted to be 2D topological insulators. The approach involves integration of fabrication and characterization techniques suitable for the study of air-sensitive materials and develops a workflow that minimizes sample fabrication to enhance throughput. Graduate and undergraduate students are involved in the development of the experimental methods which provides a comprehensive training in device fabrication, instrumentation design, and data analysis.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.