NMR Studies of Field-Induced Phases in Molecular Solids

****技术摘要****在本项目的过程中，将采用固态磁共振技术来解决与新型磁场感应相相关的问题。要研究的系统是选择具有非磁性基态的分子超导体和绝缘体，每个系统都表现出未探索和未知性质的场诱导相或现象。这些包括层状超导体中的高场相，电荷密度波/自旋-佩尔斯耦合系统中的高场相，以及候选自旋-液体系统中的场致现象或相。确定新的秩序形式，有时是预期的和长期寻求的，是该项目的主要目标，并据此选择问题和制度。在相关的努力中，电荷排序和挫折之间的联系将被探索，目标是确定一种新的自旋液体材料的途径，使用压力作为调谐参数。为这些研究选择的分子晶体的性质是唯一适用于解决的问题。将在核磁共振波谱和弛豫实验的结果中寻找相变的特征，并酌情进行补充的物理性质测量。磁共振通常是解决这些问题的理想探头，因为它能适应所需的极端条件，而且它是一种通过超精细耦合对电子环境敏感的局部探头。在可能的情况下，研究将在我们在加州大学洛杉矶分校的实验室进行，并在国家高磁场实验室（NHMFL）进行需要更高磁场的工作。该项目将支持研究生和本科生的努力，他们将为在学术或工业实验室的进一步工作做好充分准备。****非技术摘要****该项目的主要目的是创造和研究在极端条件下产生的物质的新相，例如高磁场、低温和高压。选择特定的问题和系统是因为它们具有显著的物理性质，这些物理性质往往来自具有强电子-电子相互作用的系统和低维系统。我们将研究的一个这样的例子是用强磁场稳定新型超导相。改变非热参数（磁场和压力）允许对重要的相互作用进行连续调整，这有时会导致出现的特性和相位，以及为材料的研究提供条件。大部分工作将在我们在加州大学洛杉矶分校的实验室和国家高磁场实验室使用固态核磁共振（NMR）的方法进行。核磁共振方法对所研究的原子核位置的电子环境具有局部敏感性。研究生和本科生都将执行大部分实验计划，并在此过程中发展低温、高压技术和高功率射频方法方面的专业知识，以及对材料的全面了解。每个人都将为材料相关研究或工程实验室的进一步工作做好充分准备。

****Technical Abstract****In the course of this project, solid state magnetic resonance techniques will be employed to address questions related to novel magnetic field-induced phases. The systems to be studied are selected molecular superconductors and insulators with non-magnetic ground states, each exhibiting field-induced phases or phenomena with unexplored and unknown properties. These include high-field phases in layered superconductors, in a charge density wave/Spin-Peierls coupled system, and field-induced phenomena or phases in a candidate spin-liquid system. Identification of new forms of order, sometimes expected and long-sought for is the primary aim of the project, and the problems and systems are chosen accordingly. In a related effort, an association between charge ordering and frustration will be explored, with the goal of identifying a pathway to new spin liquid materials using pressure as the tuning parameter. The properties of the molecular crystals chosen for these studies are uniquely applicable to the problems addressed. Signatures for phase transitions will be looked for in the results of NMR spectroscopy and relaxation experiments, and complimentary physical properties measurements will be undertaken as appropriate. Magnetic resonance is often an ideal probe for these problems, because of its compatibility to the required extreme conditions, and because it is a local probe sensitive to the electronic environment through the hyperfine coupling. When possible, the research will be conducted in our laboratory at UCLA, and at the National High Magnetic Field Laboratory (NHMFL) for work requiring higher magnetic fields. The project will support efforts carried out by graduate and undergraduate students alike, who will be well-prepared for further work in academic or industrial laboratories.****Non-Technical Abstract****The primary aim of this project is the creation and investigation of novel phases of matter produced under extreme conditions, such as high magnetic fields, low temperatures, and high pressures. The specific problems and systems are chosen because of remarkable physical properties that tend to emerge from systems with strong electron-electron interactions and in low-dimensional systems. One such example we will be investigating is the stabilization of novel superconducting phases by high magnetic fields. Varying the non-thermal parameters (magnetic fields and pressure) allow for a continuous tuning of the important interactions, which sometimes leads to emergent properties and phases, as well as providing the conditions under which the material can be studied. Much of the work will be carried using the methods of solid state nuclear magnetic resonance (NMR) at our laboratory at UCLA and at the National High Magnetic Field Laboratory. NMR methods are locally sensitive to the electronic environment at the site of the nucleus under study. Both graduate and undergraduate students will carry out much of the experimental program, and in so doing will develop expertise in cryogenics, high-pressure techniques, and high-power radiofrequency methods, as well as a comprehensive knowledge of materials. Each will be well-prepared for further work in materials-related research or engineering laboratories.