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，涉及热能。这个团队将研究绝对零度、没有热量的情况下发生的量子相变。与海森堡测不准原理有关的零点能量在这些跃迁中起到了热的作用。作为物理学中一种新兴的范例，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。量子相变可以极大地影响物质在令人惊讶的高温下的行为，并随着温度或磁场的变化而导致体积的特征变化。在国家科学基金会的支持下开发的一项高精度技术将用于搜索这些特征的体积变化，以便识别和更好地理解潜在的量子相变。还将寻找和研究有望在量子相变附近出现的新的物质状态。本科生参与这项工作的所有方面，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温度和磁场测试平台的公司的合作者期间。参观这些机构的学生将接触到西方学院的“大科学”环境，这是一所位于洛杉矶大都市的国家文理学院，大部分工作将在那里进行。技术摘要：该团队寻求更好地了解量子相变附近物质的性质，特别是可能出现在附近的微妙有序相。我们主要关注具有磁场诱导量子临界性的Yb和U基重费米子化合物以及相关现象，如磁性有序、新型超导电性和“隐藏有序”。量子相变附近的物理行为由与相邻态的零点能量相关的量子涨落所主导。值得注意的是，这些量子涨落会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的一个主要焦点，而热力学信息很少。这些信息对于更好地理解量子多体问题是必要的。量子相变是物理学中一种新兴的范式，它被用来解释高温超导和黑洞。主要的实验方法是使用电容式膨胀仪测量热膨胀和磁致伸缩(除了一个是由国家科学基金会支持开发的)。该团队将寻找低温下体积的特征变化，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材料表征的自动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西方学院的“大科学”环境，与“小科学”环境相辅相成。西方学院是洛杉矶大都市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.