CAREER: Microwave transmission spectroscopy of van der Waals materials

非技术摘要：我们通常认为电在管道中像水一样流动，但当电子相互作用强烈时，这种类比就失效了。这种所谓的电子在材料中的“集体行为”往往会导致令人兴奋的新的电子性质。该项目使用微波辐射来表征这些电子相。通过了解集体行为，可以围绕它开发新的技术。该项目涉及STEM本科生早期职业研究的方方面面。在物理学和工程学之间交叉列出的一门纳米制造课程，通过让本科生和研究生参与相关技术领域的研究，扩大了这项研究的影响。该项目的教育宣传部分通过与当地图书馆以及公立和私立学校的伙伴关系，侧重于大费城地区的K-12学生。这些活动让学生接触到与项目研究领域直接相关的实践STEM活动：纳米技术、电子学、低温和量子力学。技术摘要：在高度相互作用的电子系统中测量脆弱电子态的性质是一项艰巨的任务。本项目利用微波透射谱研究了范德华材料在低温和强磁场下的集体电子态，方法是将微波辐射通过相邻的共面波导耦合到二维电子系统。微波辐射的传输对载流子电导和与钉扎晶体杂质相关的固相集体振荡很敏感。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烈自旋-轨道相互作用的过渡金属二卤化物进行了比较。这项研究还将光谱技术扩展到研究二维超导体。这项研究围绕着最近被质疑的无耗散状态，该状态存在于Berezinskii-Kosterlitz-Thouless转变之下，通过测量与频率相关的电导。研究了电子和复合费米子的几个相：Wigner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。该项目解决了材料中高度相互作用的电子系统的基本问题，这些材料将推动量子电子学领域的发展，因此是广大学术界和工业界最感兴趣的问题。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。

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.