Electrodynamics of Fe-based High-Tc Superconductors

****非技术摘要****超导体是一种没有任何电阻的导电材料，这意味着当电流流过材料时不会损失能量。如果一种材料成为超导体的温度（Tc）接近室温，那么在其他应用中，使用超导传输线传输电力将是可行的。鉴于其丰富性、复杂性、对其他领域的影响以及潜在的技术重要性，当代物理学中几乎没有其他尚未解决的问题超越了高温超导问题。该个人研究者奖支持旨在在这一具有挑战性的问题上取得重大进展的项目。一套全面的红外（IR）研究最近发现的一类高tc超导体，“pnictide超导体”，将进行。该项目是由几个因素共同促成的，包括红外光学仪器的最新进展，以及新出现的具有良好特征的pnictide高tc材料单晶，这些材料非常适合解决一些长期存在的具体问题。对该项目的成功同样重要的是，致力于招募有才华的研究生加入研究小组，包括目前在科学领域代表性不足的群体的学生。后一项任务将通过参与研究本科生来完成，这些本科生的很大一部分学生属于代表性不足的群体。此外，PI将继续为加州大学圣地亚哥分校的高年级本科生和研究生提供“物理学伦理”课程。本课程的目的是从一开始就激发学生对科学工作的道德观念，从而提高学生对他们的工作对社会的巨大影响的认识。****技术摘要****这项个人研究者奖将支持对最近发现的pnictide高tc超导体进行红外研究的新努力。所提出的实验：1)将提供对粒子正常状态的基本特征的至关重要的见解，包括接近磁有序状态的作用以及移动电荷与晶格和磁激励的强耦合；2)将生成超导凝析液形成的详细实验图，包括这些各向异性体系中能量间隙和超流体密度的演化；3)将提供必要的信息，以批判性地评估电子相关在奇异的正常状态性质和超导性中的作用。该项目希望从铁基高tc超导体的整体固有特性中解开特定化合物家族的材料特定特性。这项工作将有助于培养研究生，并为本科生从事科学研究提供机会。

****NON-TECHNICAL ABSTRACT****Superconductors are materials that conduct electricity without any resistance, which means there is no loss of energy when a current flows through the material. If the temperature at which a material becomes a superconductor (its Tc) were closer to room temperature, it would be practical to use superconducting transmission lines to transfer electrical power, among other applications. The problem of high-Tc superconductivity is surpassed by few, if any, other unresolved problems in contemporary physics - in view of its richness, complexity, impact on other fields and potential technological importance. This individual investigator award supports a project aimed at making significant advances in this challenging problem. A comprehensive set of infrared (IR) studies of a recently discovered family of high-Tc superconductors, the "pnictide superconductors," will be undertaken. The project is enabled by a confluence of several factors including recent progress in the development of instrumentation for IR optics and a newly emerging availability of well characterized single crystals of pnictide high-Tc materials which are ideally suited to address a number of specific long standing issues. Equally important for the success of the project will be a dedicated effort to recruit talented graduate students into the research group, including students belonging to groups currently underrepresented in science. The latter task will be accomplished by engaging in research undergraduates from institutions with a large fraction of students belonging to underrepresented groups. Furthermore, the PI will continue offering a course on "Ethics in Physics" tailored for upper division undergraduate and graduate students at UCSD. The purpose of this course is to inspire, from the very beginning, an ethical vision of scientific work thus raising students' awareness of the tremendous impact their work can have in society.****TECHNICAL ABSTRACT****This individual investigator award will support a new effort on infrared studies of recently discovered pnictide high-Tc superconductors. The proposed experiments: 1) will deliver critically important insights into the essential characteristics of the normal state of pnictides including the role of proximity to a magnetically ordered state and strong coupling of mobile charges to both lattice and magnetic excitations; 2) will produce a detailed experimental picture of the formation of the superconducting condensate including the evolution of both the energy gap and superfluid density in these anisotropic systems; and 3) will provide information needed to critically assess the role of electronic correlations in both exotic normal state properties and superconductivity. This project expects to disentangle material-specific properties of particular families of pnictides from the intrinsic characteristics generic to the entire class of iron-based high-Tc superconductors. The work will facilitate training of graduate students and provide opportunities to engage undergraduates in scientific research.