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。在凝聚态物理学的前沿，新材料的设计和开发一直是许多基本发现的根源。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。这项NSF教师早期职业发展(CALEAR)奖支持凝聚态物理的实验研究和教育，重点是巡回电子磁铁。这个项目的主要目标是(I)设计和合成新的巡回磁性系统和(Ii)研究巡回磁性如何受到自旋涨落的影响：自旋涨落是否是这些系统中非费米液体行为的原因？巡回电子系统中产生量子临界行为的机制是什么？这些自旋波动如何打破磁性和超导等相互竞争的不稳定性的简并性？通过根据成分、压力或磁场将磁相变调整到量子临界点(QCP)，新发现的巡回磁系统将被用来回答这些基本问题中的每一个。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。PI将把她的研究专长纳入一门新的研究生水平课程，重点是磁性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，高中教师将参与国际和平协会实验室的暑期研究，这一经历反过来可以对大量学生产生巨大影响，并引导他们走向未来的科学职业生涯。非技术摘要：该奖项由2009年美国复苏和再投资法案(公共法律111-5)资助。在凝聚态物理学的前沿，新材料的设计和开发一直是许多基本发现的根源。这项NSF教师早期职业发展(CALEAR)奖支持凝聚态物理的实验研究和教育，重点是物质的新磁性状态。该项目的主要目标是：(1)设计和合成新的奇特磁性系统；(2)研究其物理性质。尽管磁性自古以来就被研究，但关于非传统磁性化合物的许多基本问题仍然没有得到解答。特别是，了解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，这是非常有兴趣的。这些相变从根本上不同于更常见的相变，例如水结冰时从液体到固体的转变。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，因为人们认为QPT中会出现非传统的超导和其他奇异的相。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。PI将把她的研究专长纳入一门新的研究生水平课程，重点是磁性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，这一经历反过来可以对大量学生产生巨大影响，并引导他们走向未来的科学职业生涯。

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.