Weak Links, Interfaces and Mechanisms of High Temperature Superconductivity

这一奖项是对威斯康星大学麦迪逊分校材料研究小组关于高温超导的弱链接、界面和机制的研究的续期资助。最初的赔偿金(DMR-8911332)提供了为期四十二个月的资金。在该奖项下进行的研究是在原奖项下开始的继续研究加上同一一般主题下的新领域的组合。有待继续的研究包括助熔剂生长的Y-BaO-CuO双晶、阳离子掺杂双晶、掺杂和非掺杂单晶、熔融处理和固态烧结多晶的耦合电磁和微结构表征，以及高速位置灵敏原子探头的开发。根据该奖项启动的新项目包括薄膜和块状超导材料图案化的局部电学和微结构耦合表征，阶跃边缘超导结的电磁和微结构耦合表征，铋-锶-钙-铜氧化物双晶晶界的电磁和微结构耦合表征，使用位置敏感原子探针研究了晶间和晶内的局部成分变化，使用高空间分辨率电子能量损失谱表征了晶界，并研究了超导带隙随温度和布里渊区位置的变化。这项研究旨在了解晶界为什么以及如何限制高温超导的输运临界电流密度。这是高温超导研究中最重要的问题之一。这项研究所需的具有挑战性的实验程序已经在材料研究小组的头三年中得到了证明。该小组是唯一一个对同一超导材料样品进行电磁和微结构耦合表征的小组。要充分发挥高温超导的潜力，提高国家技术竞争力，必须解决好临界电流密度问题。

This award is for the renewal of funding of the Materials Research Group at the University of Wisconsin at Madison on the topic of weak links, interfaces, and mechanisms of high temperature superconductivity. The original award (DMR-8911332) provided funding for a period of forty two months. The research to be performed under this award is a combination of continuation of research started under the original award plus new areas under the same general topic. Research to be continued includes coupled electromagnetic and microstructural characterization of flux-grown yttrium-barium-copper oxide bicrystals, cation-doped bicrystals, doped and undoped single crystals, melt-processed and solid state sintered polycrystals, as well as development of a high-speed position-sensitive atom probe. New programs starting under this award include coupled local electrical and microstructural characterization by patterning of thin-film and bulk-scale superconducting materials, coupled electromagnetic and microstructural characterization of step-edge superconducting junctions, coupled electromagnetic and microstructural characterization of grain boundaries in bismuth-strontium-calcium- copper oxide bicrystals, studies of local intergranular and intragranular compositional variations using the position- sensitive atom probe, characterization of the grain boundaries using high-spatial-resolution electron energy loss spectroscopy, and investigation of the superconducting gap as a function of temperature and location in the Brillouin zone. %%% The research is aimed at understanding why and how grain boundaries limit the transport critical current density of high temperature superconductivity. This is one of the most important problems in high temperature superconductivity. The challenging experimental procedures required for this research have been demonstrated in the first three years of the Materials Research Group. The group is the only one to have performed coupled electromagnetic and microstructural characterization on the same specimen of superconducting material. The issue of critical current density must be solved to achieve the full potential of high temperature superconductivity for national technological competitiveness.