Raman Spectroscopy of Quantum Spin Systems and Novel Superconductors

*强相关材料中电子之间的耦合与许多重要的科学和技术上有用的现象有关，包括超导、有序电荷和自旋密度相以及量子磁性。该项目将继续对(1)最近发现的具有重要技术意义的铁磷灰石超导体进行光谱研究，这些超导体展示了高转变温度和高临界场，(2)其他具有竞争基态的非传统超导体，以及(3)与研究强关联材料中新出现的量子力学现象相关的典型低维量子自旋系统。该项目还将为博士后和本科生提供有关低温高分辨率磁光光谱学的广泛培训。*非技术摘要*在许多新发现的材料中，电子电荷之间以及导致新的集体行为的磁矩之间存在特别强的相互作用，如超导或各种宏观上长范围有序的电荷和自旋分布相。了解这些具有强烈相互作用的材料的非常规行为是一个巨大的智力挑战，对于开发新技术至关重要。本项目将研究这些强相互作用材料的非常规性能的基本机制，通过散射来自材料的光(即“光子”)，同时通过改变温度和外部磁场来调节材料的新相来调节材料的性质。这个项目的目标是更好地理解导致这些材料新出现的性质的条件：(I)解释超导和其他非传统微观有序相的起源，(Ii)阐明物质在新的环境条件下的行为，以及(Iii)开发具有增强功能性质的新材料。对该项目的成功同样重要的是，将致力于招募有才华的本科生和研究生加入研究小组，包括属于目前在科学领域代表性不足的群体的学生。该项目还将与国际顶尖科学家进行不同的互动，并为博士后和学生提供广泛的培训，并将作为通过参观先进的激光光学实验室来吸引K-12学生对科学感兴趣的外联计划的一部分。

****TECHNICAL ABSTRACT****Coupling between electrons in ''strongly correlated materials'' is associated with many scientifically important and technologically useful phenomena, including superconductivity, ordered charge and spin density phases and quantum magnetism. This project will pursue spectroscopic studies of (1) recently discovered and technologically important superconductors from the iron-pnictide family which demonstrate high transition temperature and high critical fields, (2) other unconventional superconductors with competing ground states, and (3) prototypical low-dimensional quantum spin systems relevant for studying emerging quantum mechanical phenomena in strongly correlated materials. This project will also provide broad training to postdoc and undergraduate students in low-temperature high resolution magneto-optical spectroscopy.****NON-TECHNICAL ABSTRACT****In many newly discovered materials, there is a particularly strong interaction between the electron charges as well as between the magnetic moments leading to new collective behaviors such as superconductivity or various macroscopically long ranged ordered phases of charge and spin distributions. Understanding the unconventional behavior of these materials with strong interactions presents a great intellectual challenge and is critical to developing new technologies. This project will investigate the basic mechanisms responsible for unconventional properties of these strongly interacting materials by scattering light (i.e., "photons") from the materials while tuning the materials' properties through their novel phases by changing temperature and external magnetic fields. The goals of this project are to better understand the conditions responsible for the emerging properties of these materials: (i) explain the origin of superconductivity and other unconventional microscopically ordered phases, (ii) to elucidate how matter behaves under novel environmental conditions, and (iii) to develop new materials with enhanced functional properties. Equally important for the success of the project will be a dedicated effort to recruit talented undergraduate and graduate students into the research group, including students belonging to groups currently underrepresented in science. This project will also provide diverse interactions with leading international scientists and broad training to postdocs and students, and will be used as part of an outreach program to interest K-12 students in the sciences via tours of the advanced laser optical laboratory.