NMR Studies of Field-Induced Phases in Molecular Solids

*技术摘要*在本项目的过程中，将使用固态磁共振技术来解决与新型磁场感应相有关的问题。被研究的系统是选定的分子超导体和具有非磁性基态的绝缘体，每个系统都表现出具有未知和未知性质的场感应相或现象。这些包括层状超导体中的高场相，电荷密度波/自旋-佩耶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。确定新的订单形式，有时是预期的和长期寻求的，是该项目的主要目标，并相应地选择问题和系统。在一项相关的工作中，将探索电荷有序和受挫之间的关联，目标是确定一条使用压力作为调整参数的新自旋液体材料的途径。为这些研究选择的分子晶体的性质对于所解决的问题是唯一适用的。将在核磁共振波谱和弛豫实验的结果中寻找相变的特征，并将适当地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，因为它与所需的极端条件兼容，而且它是通过超精细耦合对电子环境敏感的局部探头。如果可能，研究将在我们位于加州大学洛杉矶分校的实验室和国家强磁场实验室(NHMFL)进行，以进行需要更高磁场的工作。该项目将支持研究生和本科生所做的努力，他们将为在学术或工业实验室中的进一步工作做好充分准备。*非技术摘要*本项目的主要目标是创造和研究在极端条件下产生的新的物质相，如强磁场、低温和高压。选择特定的问题和系统是因为具有强电子-电子相互作用的系统和低维系统中往往会出现显著的物理性质。我们将要研究的一个这样的例子是强磁场对新型超导相的稳定。通过改变非热参数(磁场和压力)，可以连续调节重要的相互作用，这有时会导致新的性质和相，并提供了研究材料的条件。大部分工作将在加州大学洛杉矶分校的实验室和国家强磁场实验室使用固态核磁共振(核磁共振)的方法进行。核磁共振方法对所研究原子核位置的电子环境是局部敏感的。研究生和本科生都将完成大部分实验计划，在这样做的过程中将发展低温、高压技术和高功率射频方法方面的专业知识，以及全面的材料知识。每个人都将为在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.