CAREER: Spin Fluctuation in Itinerant Electron Magnetic Systems

技术摘要：该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。在凝聚态物理的前沿，新材料的设计和开发是许多基础发现的根源。预测和合成目标化合物的能力是我们理解复杂固体中化学、晶体结构和物理性质之间关系的主要挑战之一。NSF教师早期职业发展（Career）奖支持凝聚态物理的实验研究和教育，重点是流动电子磁体。该项目的主要目标是(i)设计和合成新的流动磁系统和（ii）研究流动磁如何受到自旋涨落的影响：自旋涨落是否对这些系统中的非费米液体行为负责？流动电子系统中量子临界行为的机制是什么？这些自旋涨落是如何打破磁性和超导性等相互竞争的不稳定性的简并的？新发现的流动磁系统将通过组成、压力或磁场将磁相变调整到量子临界点（QCP），用于回答这些基本问题。参与该项目的本科生和研究生将接受晶体生长和表征方面的培训，这是材料驱动凝聚态研究的宝贵工具。该PI将把她的研究专长纳入一门新的研究生课程，重点关注磁学和磁性材料的现代问题。PI的实验室资源将用于说明本课程的某些方面。此外，高中教师将参与PI实验室的暑期研究，这种经历反过来会对大量学生产生巨大影响，并指导他们未来的科学事业。非技术总结：该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。在凝聚态物理的前沿，新材料的设计和开发是许多基础发现的根源。NSF教师早期职业发展（Career）奖支持凝聚态物理学的实验研究和教育，重点是物质的新型磁性态。该项目的主要目标是(i)设计和合成新的奇异磁系统和（ii）研究它们的物理性质。尽管自古以来人们就对磁学进行了研究，但关于非常规磁性化合物的许多基本问题仍未得到解答。特别是，当温度降低到接近绝对零度或接近量子相变（QPT）时，会发生什么，这是非常有趣的。这与我们更熟悉的相变有本质的不同，比如水结冰时从液体到固体的相变。在量子相变的情况下，现在起作用的是量子涨落而不是热涨落。理解这种转变和量子涨落的作用是至关重要的，因为非常规的超导性和其他奇异相被认为是从QPT中出现的。参与该项目的本科生和研究生将接受晶体生长和表征方面的培训，这是材料驱动凝聚态研究的宝贵工具。该PI将把她的研究专长纳入一门新的研究生课程，重点关注磁学和磁性材料的现代问题。PI的实验室资源将用于说明本课程的某些方面。此外，高中教师将参与PI实验室的暑期研究，这种经历反过来会对大量学生产生巨大影响，并指导他们未来的科学事业。

TECHNICAL SUMMARY: This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). At the forefront of condensed matter physics, the design and development of new materials has been the root of many fundamental discoveries. The ability to predict and synthesize targeted compounds represents one of the main challenges of our understanding of the relations between the chemistry, crystal structure and physical properties in complex solids. This NSF Faculty Early Career Development (CAREER) award supports experimental investigations and education in condensed matter physics, with focus on itinerant electron magnets. The main goals of this project are (i) the design and synthesis of novel itinerant magnetic systems and (ii) the study how itinerant magnetism is affected by spin fluctuations: Are spin fluctuations responsible for non-Fermi liquid behavior in these systems? What are the mechanisms responsible for quantum critical behavior in itinerant electron systems? How do these spin fluctuations break the degeneracy of competing instabilities like magnetism and superconductivity? By tuning the magnetic phase transitions to a quantum critical point (QCP) by composition, pressure or magnetic field, the newly discovered itinerant magnetic systems will be used to answer each of these fundamental questions. Undergraduate and graduate students involved in the project will be trained in crystal growth and characterization, valuable tools for materials driven condensed matter research. The PI will incorporate her research expertise into a new graduate-level course focused on modern problems in magnetism and magnetic materials. The PI's laboratory resources will be used to illustrate some aspects of this course. In addition, high school teachers will be involved in summer research in the PI's laboratory, an experience that, in turn, can have a great impact on a large number of students and guide them towards future careers in science.NON-TECHNICAL SUMMARY: This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). At the forefront of condensed matter physics, the design and development of new materials has been the root of many fundamental discoveries. This NSF Faculty Early Career Development (CAREER) award supports experimental investigations and education in condensed matter physics, with focus on novel magnetic states of matter. The main goals of this project are (i) the design and synthesis of novel exotic magnetic systems and (ii) the study of their physical properties. Although magnetism has been studied since antiquity, many fundamental questions remain unanswered about unconventional magnetic compounds. In particular it is of great interest to understand what happens as the temperature is lowered close to absolute zero, or towards quantum phase transitions (QPT). These are fundamentally different than the more familiar phase transitions, for example liquid-to-solid as water freezes. In the case of quantum phase transitions, quantum and not thermal fluctuations are now at play. It is crucial to understand such transitions and the role of quantum fluctuations, since unconventional superconductivity and other exotic phases are believed to emerge from QPT. Undergraduate and graduate students involved in the project will be trained in crystal growth and characterization, valuable tools for materials driven condensed matter research. The PI will incorporate her research expertise into a new graduate-level course focused on modern problems in magnetism and magnetic materials. The PI's laboratory resources will be used to illustrate some aspects of this course. In addition, high school teachers will be involved in summer research in the PI's laboratory, an experience that, in turn, can have a great impact on a large number of students and guide them towards future careers in science.