CAREER: Electrically tuned topological phase transitions in moire heterostructures

非技术摘要在分离和处理原子稀薄材料方面的最新进展为定制材料特性提供了新的方法。这种二维系统对其环境高度敏感，它们可以堆叠在一起，这样一层的性质就会影响到相邻的层。这个项目涉及将不同的材料组合在一起，这样一种材料既可以作为另一种材料的传感器，也可以调节另一种材料的电子性质。特别是，扭转一层相对于另一层会导致其中电子之间的强烈相互作用。改变附近第三层中的电子数量可以控制相互作用的强度，并可以改变电子性质，如纳米级的电荷分布。此外，相反的过程，即纳米级的电荷排列在第三层上印记可重新配置的调制，也可能导致奇异的量子行为。所预测的态可能在低功率电子学、容错量子计算和新型电磁器件中有应用。该项目还培训本科生和研究生从事量子技术的职业，建立一个介绍物理领域的非技术视频库，并通过开发和实施动手高中教学模块来激励下一代研究人员。技术摘要将范德华材料堆叠成异质结构为设计新兴电子相提供了前所未有的灵活性。本项目研究的是混合莫尔体系，在该体系中，扭曲的过渡金属二卤化物(TMD)通过薄的间隔物从双层石墨烯中分离出来。在这种几何结构中，石墨烯既可以作为传感器，也可以用来在扭曲的TMD的相关和拓扑基态之间进行调谐。这项研究的重点是热力学测量，以解决基态和激发的有序性和自旋/谷特性。主要目标包括：1)探索扭曲的TMD的拓扑相图作为位移场的函数；2)研究铁电性和新颖的Hubbard模型几何结构；3)利用TMD莫尔晶格在石墨烯上印记一个可重构的周期势来研究Hofstadter蝴蝶物理。这项研究与平行的教育目标交织在一起，包括开发演示拓扑学和几何学关键概念的教学模块，以及建立一个介绍研究子领域的非技术性视频资料库。此外，本科生、研究生和高中教师在范德华组装和低温电子测量领域获得了直接的实验室经验。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 abstractRecent advances in isolating and manipulating atomically thin materials provide new approaches to tailor material properties. Such two-dimensional systems are both highly sensitive to their environment and they can be stacked so that properties from one layer influence adjacent layers. This project involves combining dissimilar materials so that one both acts as a sensor for and can modulate the electronic properties of the other. In particular, twisting one layer relative to another induces strong interactions between the electrons in them. Modifying the number of electrons in a third nearby layer enables control over the strength of interactions and can change electronic properties such as the distribution of charge at the nanoscale. Furthermore, the reverse process, where the nanoscale charge arrangement imprints a reconfigurable modulation on the third layer, can also lead to exotic quantum behavior. The predicted states may have applications in low-power electronics, fault-tolerant quantum computing, and novel electromagnetic devices. The project also trains undergraduate and graduate students for careers in quantum technology, builds a library of non-technical videos introducing fields of physics, and inspires the next generation of researchers by developing and implementing hands-on high school instructional modules.Technical abstract Stacking van der Waals materials into heterostructures provides unprecedented flexibility to engineer emergent electronic phases. This project investigates hybrid moiré systems in which a twisted transition metal dichalcogenide (TMD) is separated from a bilayer graphene flake by a thin spacer. In this geometry, the graphene both acts as a sensor and can be used to tune among correlated and topological ground states of the twisted TMD. The research focuses on thermodynamic measurements addressing the order and spin/valley character of the ground states and excitations. Primary goals include: 1) exploring the topological phase diagram of twisted TMDs as a function of displacement field; 2) investigation of ferroelectricity and novel Hubbard model geometries; and 3) using the TMD moiré lattice to imprint a reconfigurable periodic potential on the graphene to study Hofstadter butterfly physics. The research is intertwined with parallel educational goals, including development of instructional modules demonstrating key concepts of topology and geometry, and building a library of non-technical videos introducing research subfields. In addition, undergraduates, graduate students, and high school teachers gain direct laboratory experience in the area of van der Waals assembly and low-temperature electronic measurements.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.