CAREER: Microwave transmission spectroscopy of van der Waals materials

非技术性摘要：我们通常认为电就像管道中的水一样流动，但是当电子强烈相互作用时，这种类比就不成立了。材料中电子的这种所谓的“集体行为”通常会导致令人兴奋的新电子特性。该项目使用微波辐射来表征这些电子相。通过理解集体行为，可以围绕它开发新技术。该项目涉及早期职业STEM本科研究人员在研究的各个方面。在物理学和工程学之间交叉列出的纳米实验室课程通过吸引相关技术领域的本科生和研究生来扩展这项研究的影响。该项目的教育推广部分通过与当地图书馆以及公立和私立学校的合作，重点关注大费城地区的K-12学生。这些活动使学生接触到与项目研究领域直接相关的动手STEM活动：纳米技术，电子学，低温学和量子力学。技术摘要：测量高相互作用电子系统中脆弱电子态的性质是一项艰巨的任务。本计画利用微波传输光谱学，借由将微波辐射经由相邻的共面波导耦合至二维电子系统，来研究低温及高磁场下货车德瓦耳斯材料中的集体电子态。微波辐射的传输对载流子电导率和与钉扎到晶体杂质相关联的固相的集体振荡敏感。该项目表征了石墨烯中的几种电子固体，并将这些结果与具有强自旋轨道相互作用的过渡金属二硫属化物进行了比较。这项研究还扩展了光谱技术，以研究二维超导体。本调查围绕最近质疑的无耗散状态下存在的Berezinskiii-Kosterlitz-无耗散转变通过测量频率依赖的电导。研究了电子和复合费米子的几个相：维格纳和Skyrme晶体，条纹相，超导凝聚体，超导涡旋晶格，以及可能从未见过的量子态。该项目致力于解决材料中高度相互作用电子系统前沿的基本问题，这些问题将推动量子电子学领域的发展，因此引起了广泛的学术界和工业界的最高兴趣。该奖项反映了NSF的法定使命，并被认为值得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来支持。

Nontechnical abstract: We often consider electricity as flowing like water in a pipe, but this analogy breaks down when electrons interact strongly. This so-called "collective behavior" of electrons in a material often leads to exciting new electronic properties. This project uses microwave radiation to characterize these electronic phases. By understanding the collective behavior, new technology can be developed around it. This project involves early career STEM undergraduate researchers in every aspect of the research. A nanofabrication course that is cross-listed between Physics and Engineering extends the impact of this research by engaging undergraduate and graduate students in related technical fields. Educational outreach components of this project focus on K-12 students in the greater Philadelphia area through partnerships with local libraries as well as public and private schools. These events expose students to hands-on STEM activities that are directly related to the project’s research areas: nanotechnology, electronics, cryogenics, and quantum mechanics. Technical abstract: Measuring the properties of fragile electronic states in highly-interacting electronic systems is a difficult task. This project employs microwave transmission spectroscopy to study collective electronic states in van der Waals materials at low temperatures and high magnetic fields by coupling microwave radiation to the two-dimensional electron system through an adjacent coplanar waveguide. The transmission of microwave radiation is sensitive to carrier conductivity and the collective oscillations of solid phases associated with pinning to crystal impurities. This project characterizes several electronic solids in graphene and compares these results with transition metal dichalcogenides that have strong spin-orbit interaction. The research also expands the spectroscopic technique to investigate two-dimensional superconductors. This investigation revolves around the recently-questioned dissipationless state that exists below the Berezinskii–Kosterlitz–Thouless transition by measuring the frequency-dependent conductance. Several phases of both electrons and composite fermions are studied: Wigner and Skyrme crystals, stripe phases, superconducting condensates, superconducting vortex lattices, and possibly never-before-seen quantum states. This project addresses fundamental questions at the frontiers of highly interacting electronic systems in materials that will advance the field of quantum electronics and are therefore of the highest interest to broad academic and industrial communities.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.