Pressure Tuning of Competing Quantum States

不同状态之间的转换——从固体到液体到气体，从导体到绝缘体——是经常发生的。在绝对零度的温度下，不同的物理现象出现了。量子力学起着核心作用，它改变了为经典跃迁设计的普遍反应。这可以为材料的光学响应、器件的电子特性或存储材料的磁容量带来新的可能性。该项目在三个相关领域探索模型系统的量子特性：解析磁性和超导性之间的合作和竞争，描述当电子片放置在非常高的磁场中时物质进入的新状态，以及破译绝缘体转化为金属的方式。在每一种情况下，这项研究都利用了金刚石砧细胞技术的能力，可以接触到日常技术之外的压力，并传输高能x射线。各种各样的技术，从同步加速器的x射线散射到实验室的电测量，以及将物理、化学和材料科学应用于这些研究的必要性，为学生在工业、国家实验室或学术界的职业生涯提供了很好的培训。将研究视角引入教育是另一个重点，包括与STEM教师和公众的联系。技术摘要：量子相变的影响可以在惊人的高温下感受到。许多具有重要技术意义的材料表现出不同寻常的电子、光学和磁性，这些特性归因于量子临界点的接近。然而，复杂的材料性质，与相互竞争的基态相结合，使得很难辨别基本的物理性质。此外，如果没有温度作为变量，量子临界点的研究很难接近已成为经典临界现象实验标志的精确性。该项目结合了高分辨率的纯材料研究，利用压力调节到可访问的量子临界点，揭示磁性，无序，相关材料和量子相变的基本方面。其中包括调制自旋顺序和超导性之间的竞争，排列在方形晶格上的自旋单线态的基本量子磁性，以及相关材料中从绝缘体到金属的转变。各种各样的技术，从x射线散射到磁输运，为学生在工业、国家实验室或学术界的职业生涯提供了很好的培训。金刚石砧细胞技术的进步对凝聚态物理学家和地球物理学家都很重要。支持STEM教师并帮助他们开发课程是一个优先事项。

NON-TECHNICAL ABSTRACTTransitions between different states - solid to liquid to gas, conductor to insulator - are common occurrences. At the absolute zero of temperature, different physics enters. Quantum mechanics plays a central role, altering the universal response that has been mapped out for classical transitions. This can lead to new possibilities in the optical response of materials, the electronic character of devices, or the magnetic capacity of storage materials. This project probes the quantum characteristics of model systems in three related arenas: parsing the cooperation and competition between magnetism and superconductivity, delineating the new states of matter accessed when sheets of electrons are placed in very high magnetic fields, and deciphering the way in which an insulator can be transformed into a metal. In each case, the research takes advantage of the ability of diamond anvil cell technology to access pressures outside of everyday techniques and to transmit high energy x-rays. The wide array of techniques, from x-ray scattering at a synchrotron to electrical measurements in the laboratory, and the necessity to apply physics, chemistry and materials science to these studies, trains students well for careers in industry, the national laboratories, or academia. Bringing research perspectives to education is another emphasis, including connections with STEM teachers and the general public. TECHNICAL ABSTRACTThe effects of a quantum phase transition can be felt up to surprisingly high temperatures. Many materials of technological import demonstrate unusual electronic, optical, and magnetic properties that have been ascribed to the close proximity of quantum critical points. However, complex materials properties, conflated with competing ground states, have made it difficult to discern the essential physics. Moreover, without temperature as a variable, studies of quantum critical points are hard pressed to approach the exactitude that has become the hallmark of experiments on classical critical phenomena. This project combines high-resolution studies of pure materials tuned to accessible quantum critical points using pressure to reveal fundamental aspects of magnetism, disorder, correlated materials, and quantum phase transitions. These include the competition between modulated spin order and superconductivity, the fundamental quantum magnetism of spin singlets arranged on a square lattice, and the transition from insulator to metal in a correlated material. The wide array of techniques, from x-ray scattering to magnetotransport, trains students well for careers in industry, the national laboratories, or academia. Advances in diamond anvil cell technology are important for condensed matter physicists and geophysicists alike. Supporting STEM teachers and helping them develop curricula is a priority.