Probing Cooper Pair Insulator to Superconductor Transitions in Amorphous Films

* 非技术摘要？*该项目包括对具有纳米尺度特征的材料进行实验，这些特征在冷却到接近绝对零度时表现出奇异的电学特性。 这些材料由元素Bi的薄膜组成，这些薄膜上穿孔有纳米级的蜂窝状孔阵列。没有空穴，这些薄膜通过电子形成对的过程变得“超导”，这种电子对被称为库珀对，能够在没有摩擦的情况下穿过Bi。 有了空穴，这些薄膜可以形成相反的状态：电绝缘体。 令人惊讶的是，这种绝缘体也包含库珀对。 这个项目的目标是表征这种状态的目标是确定的因素，防止库珀对超导。 对具有不同孔几何形状的图案化膜的实验将确定哪些几何特征产生新状态。 此外，技术，以削弱库珀对将被用来测试的假设，即库珀配对是必不可少的绝缘体状态的形成。 该项目的结果将增强我们对超导性的理解，特别是一些高温超导体的行为。 此外，这些调查提供了密集的培训，研究生和本科生在高科技，研究技术和前沿物理问题，从而帮助建立国家？技术劳动力。 * 技术摘要？*该项目包括在稀释制冷机温度下对超导材料的薄膜进行实验，该薄膜具有纳米级蜂窝状孔阵列。 我们的目标是表征最近发现的，新的绝缘状态，这些薄膜。这种状态包含库珀对，超导体的主要成分，但库珀对是局部的。 目标是确定负责库珀对本地化的因素。图案化的膜通过将Bi沉积到被深孔穿孔的阳极氧化铝模板上来创建。 将进行不同半径和间距的孔图案化的膜的调查，以确定影响库珀对本地化的几何因素。 此外，将进行绝缘状态如何响应于可以削弱和破坏库珀配对的磁性杂质的引入的调查，从而测试库珀配对是否对绝缘状态的形成是必不可少的。这些结果预计将影响量子超导体到绝缘体转变附近的其他系统和表现出有限电阻状态的高温超导材料的调查，例如欠掺杂铜氧化物中的赝能隙状态，其可能包含库珀对。 该项目及其活动还作为布朗大学两名研究生的博士研究培训。它使他们沉浸在凝聚态物理学的前沿问题，并帮助他们发展技术专长，使他们对工业或学术界有吸引力。

****NON-TECHNICAL ABSTRACT?****This project consists of experiments on materials patterned with nano-meter scale features that exhibit exotic electrical properties when cooled to near the absolute zero of temperature. The materials consist of films of the element Bi that have been perforated with a nano-meter scale honeycomb array of holes. Without the holes, these films become "superconducting" through a process in which the electrons form pairs, called Cooper pairs that are able to move through the Bi without friction. With the holes, these films can form into the opposite state: an electrical insulator. This insulator, surprisingly, also contains Cooper pairs. The goal of this project is to characterize this state with the objectives of determining the factors that prevent the Cooper pairs from superconducting. Experiments on films patterned with varying hole geometries will determine which geometrical characteristics produce the novel state. In addition, techniques to weaken the Cooper pairs will be employed to test the hypothesis that the Cooper pairing is essential to the formation of the insulator state. Results from this project will enhance our understanding of superconductivity and in particular, the behavior of some high temperature superconductors. In addition, these investigations provide intensive training for graduate and undergraduate students in high technology, research techniques and forefront physics issues and thus, help build the nation?s technological workforce. ****TECHNICAL ABSTRACT?****This project consists of experiments at dilution refrigerator temperatures on ultrathin films of superconducting materials, patterned with a nano-meter scale honeycomb array of holes. The goal is to characterize a recently discovered, novel insulating state of these films. This state contains Cooper pairs, the primary constituents of superconductors, but the Cooper pairs are localized. The objectives are to determine the factors responsible for the Cooper pair localization. The patterned films are created by depositing Bi onto anodized aluminum oxide templates that are perforated by deep holes. Investigations of films patterned with holes of varying radii and spacing will be performed to determine the geometrical factors influencing the Cooper pair localization. Also, investigations of how the insulating state responds to the introduction of magnetic impurities that can weaken and destroy Cooper pairing will be performed, thereby testing whether the Cooper pairing is essential to the formation of the insulating state These results are expected to impact investigations of other systems near the quantum superconductor to insulator transition and high temperature superconducting materials that exhibit states with finite resistance, such as the pseudo-gap state in under-doped cuprates, which might contain Cooper pairs. The project and its activities also serve as the PhD research training for two graduate students at Brown. It immerses them in frontier issues in condensed matter physics and helps them develop technical expertise that will make them attractive to industry or academia.