NMR studies of quantum matter under stressed conditions

摘要推进对量子材料的一般理解具有根本的兴趣和重要性，因为它提供了优化材料性能以供实际使用的能力。由于进展往往取决于对属性的操纵和控制，因此该项目的核心是开发和使用能够施加各向异性压力的设备来实现这些目标。主要的测量工具是核磁共振（NMR），结合单轴压力，在可变磁场和极低温度（1k）下应用。寻求的是稳定物质的其他难以接近的状态的证据，以及澄清用其他方法未解决的研究问题。我们的目标包括将单轴压力法应用于层状材料，到目前为止，这种方法非常有限。使用核磁共振是因为它是电子环境的局部探针，对电荷和自旋自由度都很敏感。研究生和本科生接受低温，射频和模拟技术方面的培训并获得专业知识，并有机会与美国和国外的研究小组合作，例如塔拉哈西的国家磁实验室。通过相关的合作，学生可以通过远程会议或现场访问，与具有互补专业知识的科学家进行互动，从而受益。技术摘要：该项目的目标包括进一步发展和扩大应力/应变法的应用，同时利用磁共振的能力。目的是观察、控制和理解选定量子材料中的现象和相。核磁共振非常适合这项任务，因为它是局部电荷和磁环境的探针，并且它的实现与其他实验约束兼容。通过应变调谐量子物质具有广泛应用的潜力，因为它可以在原位连续变化。这个项目的具体目标是表现出几乎简并的拓扑超导相的材料，非常规超导中未解决的问题，以及受挫的量子磁体。在这三个模型系统中，可调性的来源不同。其一，费米能量接近范霍夫奇点是关键。其次，近简并基态的相对稳定性是重要的。在第三种情况下，受挫互动的强度是被操纵的。在成功地探索了典型费米液体的正常和超导状态的物理基础上，对超导状态的进一步限制仍然是当务之急。此外，还对该方法进行了扩展，详细研究了费米液态的应变致击穿及其对物理参数和集体涨落的影响。在层状硫族化合物体系中，包括电荷密度波材料和被认为支持近简并基态的拓扑超导体，提出了该方法对范德华材料的适用性。利用应变装置调谐二维量子磁体中受挫的相互作用。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 abstractAdvancing the general understanding of quantum materials is of fundamental interest and importance, as it gives the ability to optimize materials properties for practical use. Since progress often turns on manipulation and control of properties, central to the project is the development and use of devices capable of imposing anisotropic pressure to achieve those ends. The primary measurement tool is nuclear magnetic resonance (NMR), applied in combination with the uniaxial pressure, in variable magnetic fields and to very low temperatures (1 K). Sought after is evidence for stabilization of otherwise inaccessible states of matter, and clarification of research questions unresolved by other means. Our objectives include the application of the uniaxial pressure method to layered materials where means have been quite limited until now. NMR is used because it is a local probe of the electronic environment, sensitive to both charge and spin degrees of freedom. Graduate and undergraduate students are trained and gain expertise in cryogenic, radiofrequency, and simulation technologies, with opportunities to collaborate with research groups in the United States and abroad, such as the National MagLab in Tallahassee. By way of the associated collaborations, the students benefit from interactions with scientists of complementary expertise, through remote conferencing or on-site visits.Technical abstractThe project objectives include the further development of, and broadening the use of the stress/strain method while exploiting the capabilities of magnetic resonance. The purpose is for observation, control, and understanding of phenomena and phases in selected quantum materials. NMR is well-suited for this task because it is a probe of the local charge and magnetic environment, and its implementation is compatible with the other experimental constraints. Tuning quantum matter by strain has potential for broad application, since it can be varied continuously, in situ. Specifically targeted in this project are materials exhibiting nearly degenerate topological superconducting phases, unsolved problems in unconventional superconductivity, and frustrated quantum magnets. The tunability is of a different origin in the three model systems. In one, the proximity of the Fermi energy to a van Hove singularity is key. In a second, the relative stability of nearly degenerate ground states is important. In a third, the strength of frustrated interactions are manipulated. Building on the demonstrated success in exploring the physics of the normal and superconducting states of an archetypal Fermi Liquid, further constraints on the superconducting state remains a top priority. In addition, the method is extended to study in some detail the strain-induced breakdown of the Fermi Liquid state and its influence over physical parameters and collective fluctuations. The suitability of the method to Van der Waals materials are advanced in layered chalcogenide systems, including a charge density wave material, and a topological superconductor considered to support nearly degenerate ground states. The frustrated interactions in a two-dimensional quantum magnet are tuned using the strain device.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.