CAREER: High Pressure Studies of Novel Quantum Phase Transitions

当物质从一个相调谐到另一个相时（例如磁性到非磁性，或绝缘到金属），在过渡附近经常出现意想不到的相。对表现出这种转变（被称为“量子相变”）的系统的研究不仅有可能在基本层面上推进我们对物质的理解，而且还可以提供见解，使我们能够为实际应用量身定制这些新兴的量子相。这种涌现相的一个例子是超导性。超导体表现出完全无损的电力传输，超导材料的进步对包括低损耗电力线、高效储能单元、发电机和电动机、敏感磁场探测器、高频滤波器、磁悬浮列车和计算机在内的应用具有广泛的影响。该项目的目标是利用高压来发现物质的新涌现阶段，并提高我们理解和控制这些阶段的能力。施加压力提供了一种强大的手段，可以通过各种相位快速调整单一材料。通过一个综合的外展计划，来自STEM（科学、技术、工程和数学）中代表性不足的群体的K-12学生将了解到科学可以令人兴奋，他们可以在学习物理原理的过程中获得乐趣。这种积极的经历将鼓励其中一些学生追求STEM教育和职业。本科生和研究生将通过他们的外展参与学习成为更好的科学传播者，并将在实验室接受跨学科的技术培训。***技术摘要***研究由量子而非热涨落驱动的相变是凝聚态物理的前沿之一。这样的系统表现出强烈的倾向，表现出与相互竞争的量子基态之间相互作用有关的有趣而鲜为人知的现象。通过在连续的条件范围内与理论进行比较，设计用于使用静水压力驱动材料通过量子相变的实验，为促进我们对物质的奇异相的理解做出了有力的贡献，这些奇异相有时会出现在这种转变附近。该项目的目标是进行高压实验，旨在提高我们对量子相变附近物质性质的理解。特别强调的是新型超导态的出现。该方法大致可以概括如下：(1)合成已知或可能表现出量子相变的材料的高质量单晶样品；(2)探测这些材料在高压、高磁场和低温等多种极端条件下的性能；(3)进一步改进某些高压技术，使其足够简单，可以作为样品表征的常规部分。

*** Non- Technical Abstract ***When matter is tuned from one phase to another (e.g. magnetic to non-magnetic, or insulating to metallic) unexpected phases often emerge near the transition. Studies of systems exhibiting such transitions (known as "quantum phase transitions") not only have the potential to advance our understanding of matter on a basic level, but also to provide insights that may allow us to tailor these emergent quantum phases for practical applications. One example of such an emergent phase is superconductivity. Superconductors exhibit completely lossless transmission of electricity, and advances in superconducting materials have the potential for broad impacts with applications including low-loss power lines, high efficiency energy storage units, electrical generators and motors, sensitive magnetic field detectors, high frequency filters, magnetically levitated trains, and computers. The goal of this project is to use applied high pressure to discover new emergent phases of matter and to advance our ability to understand and control these phases. Applied pressure provides a powerful means of rapidly tuning a single material through a variety of phases. Through an integrated outreach program, K-12 students from groups under-represented in STEM (Science, Technology, Engineering, and Mathematics) will learn that science can be exciting and that they can have fun learning physics principles. This positive experience will encourage some of these students to pursue STEM educations and careers. Undergraduate and graduate students will learn to become better scientific communicators through their outreach participation and will receive interdisciplinary technical training in the laboratory.*** Technical Abstract ***The study of phase transitions that are driven by quantum, rather than thermal, fluctuations represent one of the frontiers of condensed matter physics. Such systems show a strong propensity to exhibit intriguing and poorly understood phenomena associated with the interplay between competing quantum ground states. By affording comparison with theory over a continuous range of conditions, experiments designed to drive materials through quantum phase transitions using hydrostatic pressure render a potent contribution to advancing our understanding of the exotic phases of matter that sometimes emerge near such transitions. The goal of this project is to carry out high pressure experiments designed to advance our understanding of the properties of matter in the vicinity of quantum phase transitions. A particular emphasis is placed on the emergence of novel superconducting states. The approach can be broadly summarized as follows: (1) Synthesize high-quality, single-crystalline specimens of materials that are either known to or likely to exhibit quantum phase transitions, (2) Probe the properties of these materials under multi-extreme conditions of high-pressure, high magnetic fields, and low temperatures, and (3) Further refine certain high pressure techniques so that they are simple enough to perform as a routine part of sample characterization.