Materials World Network: Novel Physical Phenomena in Unusual Mesoscopic Superconductors

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。这个材料世界网络（MWN）团队由来自中国、哥伦比亚、日本、瑞士和美国的五名实验家和两名理论家组成，他们研究不寻常的、大部分未被探索的介观超导体。特别地，它1)研究具有单、双或多重连接的样品几何形状以及破坏状态的超小介观超导体；2)研究介观的常规s波超导体和/或被非常规手性p波超导体包围的正常金属；3)探索p波超导-铁磁金属-超导体（S/F/S）约瑟夫森结，了解交换和库珀配对相互作用之间的相互作用；最后，4)开展综合研究和教育活动。这项工作试图通过改变样品拓扑结构和同时缩小样品尺寸来发现新的物理现象，利用最近发现的非常规介介超导系统，或者冒险进入奇异p波S/F/S约瑟夫森结的制造和测量，这些结的戏剧性现象已经在理论上得到了预测。通过这些研究，我们期望对样品拓扑相关的介观超导性和非常规超导性，包括通过铁磁势垒的约瑟夫森耦合，获得新的见解。有待探索的介观超导系统的不寻常性质，以及它们在很大程度上未被探索的事实，似乎确保了新发现的充足机会。此外，这个MWN团队拥有不同寻常的广泛的技术专长，包括超纯单晶生长（通过漂浮区方法），先进的电子束光刻和聚焦离子束纳米制造，复杂的结构和光谱表征（z对比透射电子显微镜和低温扫描隧道显微镜和光谱），高度专业化的器件制造（SFS Josephson结），和低温测量（稀释-冰箱温度）。在理论方面，我们的团队包括计算建模、现象学和微观理论方面的专家。本研究为介观超导体在未来的技术应用奠定了基础，也为研究和教育的有意义整合提供了有效的工具，旨在为我们的研究生和本科生提供一个国际化的学习和研究环境。这个项目有助于从众多的女性和少数族裔学生中吸引更多的人才来从事物理科学方面的职业。除了通过学生交流和国际合作伙伴的访问，为学生提供在多机构，多文化环境下的研究经验外。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). This Materials World Network (MWN) team consists of five experimentalists and two theorists from China, Colombia, Japan, Switzerland, and the US to investigate unusual, mostly unexplored mesoscopic superconductors. In particular it 1) studies ultrasmall mesoscopic superconductors that feature a singly, doubly, or multiply connected sample geometry as well as a destructive regime; 2) investigates mesoscopic, conventional s-wave superconductor, and/or a normal metal bordered by an unconventional, chiral p-wave superconductor; 3) explores p-wave superconductor-ferromagnetic metal-superconductor (S/F/S) Josephson junctions to understand the interplay between exchange and Cooper pairing interactions; and finally, 4) pursues integrated research and education activities. This work seeks to uncover novel physical phenomena by varying the sample topology and shrinking the sample size simultaneously, making use of recently discovered unconventional mesoscopic superconducting systems, or venturing into the fabrication and measurement of exotic p-wave S/F/S Josephson junctions for which dramatic phenomena have been predicted theoretically. Through these studies we expect to obtain new insights into sample-topology dependent mesoscopic superconductivity and unconventional superconductivity including Josephson coupling through a ferromagnetic a barrier. The unusual nature of the mesoscopic superconducting systems to be explored and the fact that they have largely been unexplored previously appear to ensure ample opportunities for new discoveries. In addition, this MWN team possesses an unusually wide range of technical expertise including ultrapure single crystal growth (by floating zone method), advanced e-beam lithography and focused ion beam nanofabrication, sophisticated structural and spectroscopic characterization (Z-contrasted transmission electron microscopy and low-temperature scanning tunneling microscopy and spectroscopy), highly specialized device fabrication (SFS Josephson junctions), and low-temperature measurements (dilution-refrigerator temperatures). On the theoretical side, our team includes specialists on computational modeling, phenomenology, and microscopic theories. This research lays a foundation for using mesoscopic superconductors for future technological applications and also serves as an effective vehicle for meaningful integration of research and education aiming at providing our graduate and undergraduate students an international environment for learning and research. This program helps attract more talents from the vast pool of woman and minority students to pursue a career in physical sciences. In addition to providing our students research experience in a multi institution, multi-culture environment through student exchange and the visits of our international collaborators.