RUI: Fluctuations and Phase Transitions in Iron Pnictide Superconductors

****技术摘要****支持本科院校低温物理实验研究。电压电流曲线的标度分析是研究正常超导相变的重要工具。然而，最近的工作表明，该工具的传统应用过于灵活，无法唯一地确定关键参数，并且外部影响可能模糊或破坏相变。在此基础上，我们成功地将该技术应用于空穴掺杂铜YBa2Cu3O7和电子掺杂铜Pr2-xCexCuO4的研究。该项目将使用相同的技术来研究新的镍铁-122超导体（SrFe2As2和BaFe2As2）在磁场和零磁场下的相变。这项工作将导致对这种材料中控制相变的模型的理解，以及铁镍超导体与其他超导体之间相变的异同。该项目还将培养实验和低温物理方面的本科生，为研究生工作或工业生涯做准备。此外，为了鼓励更广泛的科学教育，该项目将为当地公立学校现有的外展计划做出贡献，并向YouTube提交视频演示。****非技术摘要****支持本科院校低温物理实验研究。“高温”超导体是在25年前被发现的，它仍然有着巨大的希望和巨大的挑战。希望在于最终制造出具有更高转变温度的超导体，而挑战在于，即使在25年后，我们也没有完全理解这些材料是如何或为什么超导的。2008年发现的由铁和砷制成的超导体，是一系列显示出超导性的不寻常材料中最新的一种。这个个人研究者奖支持一个项目，该项目将研究铁和砷基材料如何成为超导材料，并将它们与铜氧基超导体和传统的单元素超导体进行比较，所有这些都是为了了解在这些材料中产生超导性的潜在机制。提出的研究将增加对高温超导体的了解，并有助于实现获得更高转变温度的承诺。该项目还将培训本科生掌握最先进的样品生长、表征和测量技术。该项目还将通过促进对当地学校的科学推广和通过在线视频演示促进研究，为更广泛的教育目标做出贡献。

****Technical Abstract****This award supports experimental low-temperature physics research at an undergraduate institution. The scaling analysis of voltage vs. current curves has been an invaluable tool in the study of the normal-superconducting phase transition. However, recent work has shown that the conventional application of this tool is too flexible to uniquely determine the critical parameters, and that extrinsic effects can obscure or destroy the phase transition. With these caveats known, we have successfully applied this technique to study the hole-doped cuprate YBa2Cu3O7 and the electron-doped cuprate Pr2-xCexCuO4. This project will use the same technique to examine the phase transition in the new iron pnictide-122 superconductors (SrFe2As2 and BaFe2As2) both in a magnetic field and in zero magnetic field. This work will lead to an understanding of the model that governs the phase transition in this material and the differences and similarities of the phase transition between iron pnictide superconductors and other superconductors. This project will also train undergraduate students in experimental and low-temperature physics in preparation for graduate work or industry careers. In addition, to encourage broader education in science, this project will contribute to an existing outreach program with local public schools and submit video demonstrations to YouTube.****Non-Technical Abstract****This award supports experimental low-temperature physics research at an undergraduate institution. "High-Temperature" superconductors, discovered more than a quarter of a century ago, still hold great promise and great challenges. The promise lies in the hope of eventually making superconductors with much higher transition temperatures, and the challenges lie in the fact that we do not, even 25 years later, fully understand how or why these materials superconduct. Superconductors made from iron and arsenic, discovered in 2008, are the latest in an array of unusual materials to display superconductivity. This individual investigator award supports a project that will study how iron- and arsenic-based materials become superconducting, comparing them to copper-oxygen based superconductors and conventional, single element superconductors, all in the hopes of understanding the underlying mechanism that creates superconductivity in these materials. The proposed studies will add to the knowledge of high-temperature superconductors and help fulfill the promise of attaining higher transition temperatures. This project will also train undergraduate students in state-of-the-art sample growth, characterization, and measurement techniques. This project will also contribute to broader educational goals by fostering science outreach to local schools and promoting the research via online video demonstrations.