Probing Cooper Pair Insulator to Superconductor Transitions in Amorphous Films

探测非晶薄膜中库珀对绝缘体到超导体的转变

• 批准号: 0907357
• 负责人: James Valles
• 金额: $ 40万
• 依托单位: Brown University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-11-01 至 2014-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0907357&HistoricalAwards=false
• 关键词: Probing; Cooper; Pair; Insulator; Superconductor

****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.

****非技术摘要？****该项目包括对具有纳米级特征图案的材料进行的实验，这些特征在冷却到接近绝对零温度时表现出奇异的电特性。 该材料由 Bi 元素薄膜组成，薄膜上开有纳米级蜂窝状孔阵列。没有空穴，这些薄膜通过电子形成对（称为库珀对）的过程而变得“超导”，它们能够在没有摩擦的情况下穿过Bi。 有了这些孔，这些薄膜可以形成相反的状态：电绝缘体。 令人惊讶的是，该绝缘体还包含库珀对。 该项目的目标是描述这种状态的特征，以确定阻止库珀对超导的因素。 对具有不同孔几何形状图案的薄膜进行的实验将确定哪些几何特征产生新的状态。 此外，将采用削弱库珀对的技术来检验库珀对对于绝缘体状态的形成至关重要的假设。 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，这些调查为研究生和本科生提供高科技、研究技术和前沿物理问题方面的强化培训，从而有助于建设国家的技术劳动力。 ****技术摘要？****该项目包括在稀释冰箱温度下对超导材料超薄膜进行实验，薄膜上有纳米级蜂窝状孔阵列图案。 目标是表征最近发现的这些薄膜的新颖绝缘状态。这种状态包含库珀对，这是超导体的主要成分，但库珀对是局域化的。 目标是确定导致库珀对本地化的因素。图案薄膜是通过将 Bi 沉积到带有深孔的阳极氧化铝模板上而形成的。 对具有不同半径和间距的孔图案的薄膜进行研究，以确定影响库珀对定位的几何因素。 此外，还将研究绝缘态如何响应可削弱和破坏库珀配对的磁性杂质的引入，从而测试库珀配对是否对于绝缘态的形成至关重要。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以及表现出有限电阻状态的高温超导材料的研究，例如欠掺杂中的赝带隙态 铜酸盐，其中可能包含库珀对。 该项目及其活动也作为布朗大学两名研究生的博士研究培训。它让他们沉浸在凝聚态物理的前沿问题中，并帮助他们发展技术专业知识，使他们对工业界或学术界有吸引力。