Superconducting and Metal-Insulator Transitions in Quasi-Two-Dimensional Strongly Correlated Materials

非技术：许多具有潜在重大技术意义的新材料的电子特性是由载流子之间的相互作用决定的。这些相关性产生了各种各样的现象，包括物质新状态的出现和不同相之间的转变，例如金属到绝缘体或超导体到正常。然而，这些转变背后的微观机制和这些强相关系统中各个阶段的性质还没有得到很好的理解。本研究通过在广泛的温度和磁场范围内进行电荷传输的测量，解决了两类层状强相关材料，氧化铜高温超导体和一系列新的有机系统中超导和金属绝缘体转变的基本问题。该项目的结果对于理解强相关物质至关重要，这将最终影响科学技术的发展，从而造福社会。该项目的一个关键组成部分是教育和培训研究生未来在学术界、国家实验室和工业界的职业生涯。它还包括各种活动，以扩大代表性不足的群体在科学、技术、工程和数学领域的参与，向公众推广，以及对研究基础设施的影响。技术：该项目解决了强相关材料物理学中的几个基本问题，如非常规超导性和准二维系统中的莫特金属-绝缘体跃迁。由于异常输运性质是强相关材料的关键特征之一，实验涉及电输运，包括时间分辨协议。研究主要集中在两类准二维体系，铜酸盐和新合成的准二维取代系列有机物。在这两种情况下，非常规的超导性分别是通过改变掺杂压力或化学压力来调整莫特跃迁的结果。在铜酸盐中，目标是探索高磁场对超导性的破坏，并阐明自旋和电荷有序度、无序度和量子相位涨落作为掺杂函数的各自作用。在有机物中，重点是通过探索热调谐和磁场调谐超导转变来理解非常规超导性。此外，利用时间分辨技术探讨了Mott金属-绝缘体跃迁和自旋液体激发的作用。从这个项目中获得的知识对于凝聚态物理的进一步发展是必不可少的。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。

NONTECHNICAL:Electronic properties of many new materials with potentially great technological importance are dominated by interactions among charge carriers. Those correlations give rise to a variety of phenomena, including the emergence of novel states of matter and transitions between different phases, such as metal to insulator or superconductor to normal. However, microscopic mechanisms underlying these transitions and the nature of various phases in such strongly correlated systems are not well understood. This research addresses fundamental questions about superconducting and metal-insulator transitions in two classes of layered, strongly correlated materials, copper-oxide high-temperature superconductors and a new series of organic systems, by performing measurements of charge transport over a wide range of temperatures and magnetic fields. The results of this project are crucial for understanding of strongly correlated materials, which will benefit society by ultimately influencing the development of science and technology. A key component of the project is education and training of graduate students for future careers in academia, national laboratories, and industry. It also incorporates various activities to broaden the participation of underrepresented groups in the areas of science, technology, engineering, and mathematics, outreach to general public, and impact on research infrastructure.TECHNICAL:This project addresses several fundamental questions in the physics of strongly correlated materials, such as unconventional superconductivity and the Mott metal-insulator transition in quasi-two-dimensional systems. Since anomalous transport properties are one of the key characteristics of strongly correlated materials, experiments involve electrical transport, including time-resolved protocols. Studies focus on two classes of quasi-two-dimensional systems, cuprates and newly synthesized substitutional series of quasi-two-dimensional organics. In both cases, unconventional superconductivity emerges as a result of tuning through the Mott transition by varying doping or chemical pressure, respectively. In cuprates, the goal is to probe the destruction of superconductivity by high magnetic fields and to clarify the respective roles of spin and charge orders, disorder, and quantum phase fluctuations, as a function of doping. In organics, the focus is on understanding unconventional superconductivity by exploring both thermal and magnetic-field-tuned superconducting transitions. In addition, the Mott metal-insulator transition and the role of spin liquid excitations are probed using time-resolved techniques. The knowledge gained from this project is essential for further development of condensed matter physics.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.