CAREER: Electrically tuned topological phase transitions in moire heterostructures

在分离和操纵原子薄材料方面的最新进展提供了定制材料特性的新方法。这种二维系统对环境高度敏感，并且可以堆叠，以便一层的特性影响相邻层。这个项目涉及到结合不同的材料，这样一种材料既可以作为传感器，又可以调节另一种材料的电子特性。特别是，相对于另一层扭曲一层会引起其中电子之间的强烈相互作用。修改第三层附近的电子数量可以控制相互作用的强度，并可以改变电子特性，如纳米尺度上的电荷分布。此外，相反的过程，即纳米级电荷排列在第三层上刻印可重构调制，也可能导致奇异的量子行为。预测的状态可能在低功耗电子产品、容错量子计算和新型电磁器件中得到应用。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的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，为设计涌现的电子相提供了前所未有的灵活性。本项目研究了一种混合涡流系统，在这种系统中，一种扭曲的过渡金属二硫化物（TMD）通过一层薄薄的间隔层从双层石墨烯薄片中分离出来。在这种几何结构中，石墨烯既可以作为传感器，也可以用于在扭曲TMD的相关基态和拓扑基态之间进行调谐。研究的重点是热力学测量，以解决基态和激发的顺序和自旋/谷特性。主要目标包括：1)探索扭曲tmd作为位移场函数的拓扑相图；2)铁电性和新哈伯德模型几何的研究；3)利用TMD莫尔晶格在石墨烯上刻印可重构周期势，研究霍夫施塔特蝴蝶物理。这项研究与平行的教育目标交织在一起，包括开发展示拓扑和几何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视频库。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直接的实验室经验。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。

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.