RUI: Dilatometric Studies of Quantum Criticality in F-Electron Systems

非技术摘要：普通的相变，如水的冻结或沸腾，都涉及热能。这个团队将研究在绝对零度没有热量的情况下发生的量子相变。零点能量，与海森堡测不准原理相联系，在这些转变中起着热的作用。在物理学中，量子相变可能是高温超导的起源，并为黑洞理论提供了信息。量子相变可以在惊人的高温下显著影响物质的行为，并随着温度或磁场的变化导致体积的特征变化。在美国国家科学基金会的支持下，一项高精度技术将用于寻找这些体积特征变化，以识别和更好地理解潜在的量子相变。预计在量子相变附近发生的物质的新状态也将被寻找和研究。本科生参与这项工作的各个方面，无论是在校园内，还是在访问研究型大学、国家实验室和一家制造用于材料表征的自动化温度和磁场测试平台的公司的合作伙伴期间。访问这些机构的学生将接触到一个“大科学”环境，以补充西方学院（Occidental College）的“小科学”环境。西方学院是位于洛杉矶大都会的一所国立文理学院，大部分工作将在这里进行。技术摘要：该团队寻求更好地理解物质在量子相变附近的性质，特别是在量子相变附近可能出现的微妙有序相。我们的主要焦点是基于Yb和u的重费米子化合物，它们表现出磁场诱导的量子临界性和相关现象，如磁有序、新型超导性和“隐藏秩序”。量子相变附近的物理行为是由与相邻状态的零点能量相关的量子涨落所支配的。值得注意的是，这些量子涨落可以在远高于绝对零度的温度下影响物理行为。低温相变和与之相关的量子相变是凝聚态物理学的一个主要焦点，热力学信息是稀疏的。这些信息对于更好地理解量子多体问题是必需的。量子相变是物理学中一个新兴的范式，被用来解释高温超导性和黑洞。主要的实验方法是用电容式膨胀计测量热膨胀和磁致伸缩（除了一个以外，其他都是在美国国家科学基金会的支持下开发的）。该团队将在低温下寻找体积的特征变化，以识别和更好地理解潜在的量子相变。这项工作是与研究型大学、国家实验室和一家制造用于材料表征的自动化温度和磁场测试平台的公司的科学家合作进行的。访问这些机构的本科生将接触到一个“大科学”环境，以补充西方学院（Occidental College）的“小科学”环境。西方学院是位于洛杉矶大都会的一所国立文理学院，大部分工作将在那里进行。

Non-Technical Abstract:Ordinary phase transitions, such as the freezing or boiling of water, involve heat energy. This team will study quantum phase transitions that occur at absolute zero where there is no heat. Zero-point energy, associated with the Heisenberg uncertainty principle, plays the role of heat in these transitions. A rising paradigm in physics, quantum phase transitions may be the origin of high-temperature superconductivity and have informed the theory of black holes. Quantum phase transitions can dramatically affect the behavior of matter at surprisingly high temperatures and lead to characteristic changes in volume as the temperature or magnetic field changes. A high-precision technique, developed with National Science Foundation support, will be used to search for these characteristic changes in volume in order to identify and better understand the underlying quantum phase transition. Novel states of matter that are expected to occur near quantum phase transitions will be sought out and studied as well. Undergraduate students participate in all aspects of this work, both on-campus and during trips to visit collaborators at research universities, national laboratories, and a company that manufactures automated temperature and magnetic field testing platforms for materials characterization. Students visiting these institutions are exposed to a "big science" environment complementing the "small science" environment at Occidental College, a national liberal arts college in metropolitan Los Angeles where most of the work will be carried out.Technical Abstract: Theh team seeks a better understanding of the nature of matter near quantum phase transitions, especially the delicate ordered phases that can appear nearby. Our primary focus is on Yb- and U-based heavy fermion compounds exhibiting magnetic-field induced quantum criticality and related phenomena such as magnetic order, novel superconductivity, and "hidden order." Physical behavior near a quantum phase transition is dominated by quantum fluctuations associated with the zero-point energies of the adjacent states. Remarkably, these quantum fluctuations can affect physical behavior at temperatures well above absolute zero. Low temperature phase transitions and the quantum phase transitions associated with them are a major focus of condensed matter physics, a focus on which thermodynamic information is sparse. Such information is needed for a better understanding of quantum many-body problems. A rising paradigm in physics, quantum phase transitions are invoked in explanations of high temperature superconductivity and black holes. The primary experimental method is to measure thermal expansion and magnetostriction using capacitive dilatometers (all but one developed with National Science Foundation support). The team will search for characteristic changes in volume at low temperatures in order to identify and better understand the underlying quantum phase transition. This work is carried out in collaboration with scientists at research universities, national laboratories, and a company that manufactures automated temperature and magnetic field testing platforms for materials characterization. Undergraduate students visiting these institutions will be exposed to a "big science" environment complementing the "small science" environment at Occidental College, a national liberal arts college in metropolitan Los Angeles where most of the work will be carried out.