Weak Links, Interfaces and Mechanisms of High Temperature Superconductivity

该奖项是为了更新威斯康星大学麦迪逊分校材料研究小组关于弱链接、界面和高温超导机制的研究经费。最初的合同（DMR-8911332）提供了为期42个月的资金。在该奖项下进行的研究是对原奖项下开始的研究的延续，以及在同一一般主题下的新领域的结合。接下来的研究包括磁通生长钇钡铜氧化物双晶、阳离子掺杂双晶、掺杂和未掺杂单晶、熔融加工和固态烧结多晶的耦合电磁和微观结构表征，以及高速位置敏感原子探针的开发。根据该奖项启动的新项目包括通过薄膜和大规模超导材料的图图化耦合局部电学和微结构表征，阶梯边缘超导结的耦合电磁和微结构表征，铋-锶-钙-氧化铜双晶中晶界的耦合电磁和微观结构表征，利用位置敏感原子探针研究局部晶间和晶内成分变化，利用高空间分辨率电子能量损失谱表征晶界，以及研究超导间隙与温度和布里渊区位置的关系。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前三年得到了证明。该小组是唯一一个在同一超导材料样品上进行耦合电磁和微观结构表征的小组。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.