Investigating quantum critical and topological dynamics in f-electron materials

非技术摘要：基于镧系元素和氡系元素的材料包含了丰富的新的和新的性质，具有基本的科学兴趣和在当前和未来技术中的潜在应用。这些f电子量子材料可以在元素周期表中找到，这些元素以La和Ac开始。在这里，我们寻找基于镧系元素和榄系元素的新量子材料。这特别包括含有Ce、Pr、Sm、Eu、Yb和铀的材料。将继续对物理特性和基本物理进行详细调查，主要目标是确定与技术有关的基本利益和显著现象的特征。预计这些研究将产生推动技术应用的新材料。这包括热电制冷和发电、磁热制冷、磁传感器、磁信息存储、量子计算、电子产品的高温超导、磁共振成像以及电能的产生、传输和存储。该方案有助于教育和培训博士后学者以及研究生和本科生，其中一些人来自代表性不足的群体。他们和他们的小组成员参与了社区推广活动，包括高中和本科生的实验室参观，当地小学的科学演示，以及大众讲座。技术摘要：基于镧系元素和鳗系元素的f电子量子材料包含丰富的相关电子相和现象，包括价态涨落、重费米子行为、近藤绝缘体行为、量子临界、非费米液体行为、金属-绝缘体转变、非传统超导、磁序和电荷顺序以及拓扑现象。通过改变非热控制参数，如化学成分、压力和磁场，可以“调节”竞争相互作用，从而产生包含大量相关电子相和现象的复杂相图。特别令人感兴趣的是发生在量子临界点附近的非常规超导、奇异磁相和非费米液体的物理性质，在这个临界点上，二级相变(通常是反铁磁)被抑制到0K。所提出的研究的目的是表征这些特殊的相和现象，确定它们形成的条件，确定潜在的微观机制，并检验适当的理论。该方法包括材料合成(特别是单晶)和测量这些材料的输运、热和磁性随温度、组成和磁场的变化。这与使用超快光学光谱的准粒子动力学测量相补充，提供了一种强大的手段来询问和在时间上解开电荷、自旋、晶格和轨道的自由度。将调查一系列相关的f电子材料，如填充的Skutterudite化合物和近藤绝缘体Sm-Bide(相关电子拓扑绝缘体的候选材料)及其合金。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Nontechnical Abstract: Lanthanide- and actinide-based materials comprise a rich reservoir of new and novel properties of fundamental scientific interest and potential applications in current and future technologies. These f-electron quantum materials are found in the periodic table of the elements starting with lanthanum and actinium. Here we search for new quantum materials based on lanthanide and actinide elements. This specifically includes materials containing cerium, praseodymium, samarium, europium, ytterbium and uranium. Detailed investigations of the physical properties and underlying physics will be pursued with the primary goal of characterizing the striking phenomena of fundamental interest and relevance to technology. These studies are expected to yield new materials that will advance technological applications. This includes thermoelectric cooling and electrical power generation, magnetocaloric refrigeration, magnetic sensors, magnetic information storage, quantum computing, and high temperature superconductivity for electronics, magnetic resonance imaging, and the generation, transmission, and storage of electrical energy. This program contributes to the education and training of postdoctoral scholars and graduate and undergraduate students, some of which are from underrepresented groups. The PI's and their group members are involved in community outreach activities, including laboratory tours for high school and undergraduate students, science demonstrations at local elementary schools, and popular lectures.Technical Abstract: Lanthanide- and actinide-based f-electron quantum materials comprise a rich reservoir of correlated electron phases and phenomena, including valence fluctuations, heavy fermion behavior, Kondo insulator behavior, quantum criticality, non-Fermi liquid behavior, metal-insulator transitions, unconventional superconductivity, magnetic and charge order, and topological phenomena. Competing interactions can be "tuned" by varying non-thermal control parameters such as chemical composition, pressure, and magnetic field, leading to complex phase diagrams containing a multitude of these correlated electron phases and phenomena. Of particular interest are unconventional superconductivity, exotic magnetic phases and non-Fermi liquid behavior in low temperature physical properties that occur in the vicinity of a quantum critical point where a second order phase transition (usually, antiferromagnetic) is suppressed to 0 K. The objectives of the proposed research are to characterize these extraordinary phases and phenomena, determine the conditions under which they are formed, identify underlying microscopic mechanisms, and test appropriate theories. The approach involves materials synthesis (particularly single crystals) and measurement of the transport, thermal, and magnetic properties of these materials as a function of temperature, composition and magnetic field. This is complemented with quasiparticle dynamics measurements using ultrafast optical spectroscopy, providing a powerful means to interrogate and temporally disentangle charge, spin, lattice, and orbital degrees of freedom. A broad range of correlated f-electron materials such as filled skutterudite compounds and the Kondo insulator samarium boride, a candidate for a correlated electron topological insulator, and its alloys will be investigated.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.