CAREER: Crystalizing electrons in coupled atomically thin semiconductors

该奖项全部或部分由《2021年美国救援计划法案》（公法117-2）资助。非技术描述：最常见的物质相是气体、液体和固体。就像蒸汽可以凝聚成结晶固体一样，半导体中的电子在低温下也可以自我排列成周期性图案，即晶体。尽管早在80多年前就有人预测到这种电子结晶，但实现和观察这种电子结晶仍具有挑战性。该项目研究了二维（2D）材料中电子固体的形成和熔化，这些材料只有几个原子厚。这种二维材料可以以不同的组合和方向堆叠在一起，这对电子的行为有很大的影响。该项目研究了通过控制耦合二维半导体的堆叠来促进电子结晶的方法。该研究还开发了利用量子波动可控地熔化电子晶体的方法，为量子计算和通信的新设备铺平了道路。该项目的一个组成部分是为高中生、本科生和研究生提供在前沿材料和光学实验室进行实践研究的机会。通过与当地高中和国家非营利组织的合作，该项目还针对科学和工程领域代表性不足的群体建立了实习和指导计划。该项目由材料研究部（DMR）的电子与光子材料（EPM）和凝聚态物理（CMP）项目共同资助。技术描述：维格纳晶体的研究对于理解电子相关和量子涨落之间的竞争如何在相关电子材料中产生奇异性质至关重要。最近的实验报道，当两个过渡金属二硫化物单层彼此靠近时，形成的双层维格纳晶体的稳定性显著增强。本项目旨在建立新的系统和方法来询问维格纳晶体的量子相变，从而为量子电子和光电子器件提供一个平台。本项目通过制造基于过渡金属二硫族化物的耦合双层异质结构，研究了材料的原子结构如何影响电子晶体的稳定性。这项工作的核心是发展定量方法来研究维格纳晶体相的晶格结构和动力学。通过利用量子相变的电气控制，该项目探索了新的相关相，如电子玻璃。研究活动阐明了多体量子系统中的相竞争，为下一代电子和光学器件的研究奠定了基础。该项目的一个特别重点是通过与当地高中、大学以及国家非营利组织合作，从代表性不足的群体中扩大参与者。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。

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2). Nontechnical Description: The most commonly known phases of matter are gas, liquid, and solid. Just as vapor can condense into a crystalline solid, electrons in a semiconductor can self-arrange into a periodic pattern, a crystal, at low temperatures. Although predicted more than eight decades ago, such crystallization of electrons is challenging to realize and observe. This project investigates the formation and melting of electron solids in two-dimensional (2D) materials that are only a few atoms thick. Such 2D materials can be stacked together in different combinations and orientations, which strongly influences how electrons behave. The project studies ways to promote electron crystallization by controlling the stacking of coupled 2D semiconductors. The research also develops methods to controllably melt electron crystals using quantum fluctuations, paving the way for new devices for quantum computing and communications. An integral part of the project is to provide high-school, undergraduate, and graduate students with hands-on research opportunities in leading-edge materials and optics labs. In collaboration with local high schools and national non-profit organizations, the project also establishes internship and mentorship programs targeting underrepresented groups in science and engineering. This project is jointly funded by the Electronic and Photonic Materials (EPM) and the Condensed Matter Physics (CMP) programs of the Division of Materials Research (DMR). Technical Description: The study of Wigner crystals is critical for understanding how the competition between electron correlation and quantum fluctuations gives rise to exotic properties in correlated electron materials. Recent experiments reported the formation of bilayer Wigner crystals with significantly enhanced stability when two transition metal dichalcogenide monolayers are placed close to each other. This project aims to establish new systems and methods to interrogate the quantum phase transitions of Wigner crystals to enable a platform for quantum electronic and optoelectronic devices. By fabricating coupled bilayer heterostructures based on transition metal dichalcogenides, the project investigates how the atomic structures of the materials influence the stability of the electron crystals. Central to this effort is developing quantitative approaches to investigate the lattice structures and dynamics in the Wigner crystal phase. By exploiting the electrical control of quantum phase transitions, the project explores novel correlated phases such as electron glasses. The research activities elucidate phase competition in many-body quantum systems and paves the way for next-generation electronic and optical devices. A particular focus of the project is to broaden the participants from underrepresented groups by collaborating with local high schools, universities, as well as national non-profit organizations.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.