Tunneling and Transport in Ordered and Disordered Superconductors

有序和无序超导体中的隧道效应和输运

• 批准号: 0455121
• 负责人: Allen Goldman
• 金额: $ 58万
• 依托单位: University of Minnesota-Twin Cities
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-04-01 至 2010-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0455121&HistoricalAwards=false
• 关键词: Tunneling; Transport; Ordered; Disordered; Superconductors

The main focus of this program is on the superconductor-insulator (SI) transition in ultra-thin films, an example of a quantum phase transition (QPT). Such transitions occur at zero temperature in response to the tuning of an external parameter of a system that alters its quantum mechanical ground state. They are studied through measurements at nonzero temperature of properties influenced by quantum fluctuations associated with the transition. Although many systems exhibit QPTs, including two-dimensional electron gases, and strongly correlated electron materials including high temperature superconductors, the SI transition is most fundamental because of its connection with the phase-number uncertainty relation of quantum mechanics. The nature of the physics of the SI transition has become uncertain, as in some work evidence of an intermediate metallic regime separating the superconducting and insulating ground states has emerged. It is the goal of this program to resolve the nature of the underlying physics through careful measurements of thermodynamic and electrical transport properties of films at ultra-low temperatures. Research and education are integrated in this program through the training of Ph.D. students, and research experiences for undergraduates and high school students. Some of the sample structures studied have a potential for technological significance. %%%The main focus of this program is on the investigation of the superconductor-insulator (SI) transition in ultrathin films of metals. This transition is a quantum phase transition (QPT). In contrast with ordinary phase transitions, which are tuned by temperature, QPTs are tuned by external parameters, such as magnetic field or charge density, and are found at absolute zero. They are studied through measurements at nonzero, but low temperatures, of properties influenced by proximity to the transition both in temperature and in the value of the tuning parameter. Other systems exhibiting QPTs include two-dimensional electron gases, and correlated electronic materials, including high temperature superconductors. The SI transition is one of the most fundamental of QPTs because of its connection with the uncertainty principle of quantum physics. It is the goal of this program to resolve the nature of the underlying physics of the SI transition through measurements of thermodynamic and electrical transport properties at ultra-low temperatures. Research and education are integrated in his program through the training of Ph.D. students in physics as well as by providing research experiences for younger students. Some of the configurations studied could be important in electronics technology.

该计划的主要重点是超薄膜中的超导体-绝缘体（SI）转变，这是量子相变（QPT）的一个例子。这种转变发生在零温度下，响应于改变其量子力学基态的系统的外部参数的调谐。它们是通过在非零温度下测量与过渡相关的量子涨落影响的性质来研究的。虽然许多系统都表现出QPT，包括二维电子气体和强关联电子材料，包括高温超导体，但SI跃迁是最基本的，因为它与量子力学的相数不确定性关系有关。SI跃迁的物理性质已经变得不确定，因为在一些工作中出现了将超导和绝缘基态分开的中间金属状态的证据。该计划的目标是通过仔细测量超低温下薄膜的热力学和电输运性质来解决基础物理的性质。研究和教育是通过博士的培训整合在这个程序。学生，并为本科生和高中生的研究经验。研究的一些样品结构具有潜在的技术意义。该计划的主要重点是在超导体-绝缘体（SI）过渡的金属薄膜的研究。这种转变是量子相变（QPT）。与普通的相变，这是调谐的温度，QPT是调谐的外部参数，如磁场或电荷密度，并在绝对零度。他们研究通过测量在非零，但在低温下，接近过渡的温度和调谐参数的值的影响的属性。其他表现出QPT的系统包括二维电子气体和相关电子材料，包括高温超导体。SI跃迁是QPT中最基本的跃迁之一，因为它与量子物理的不确定性原理有关。该计划的目标是通过测量超低温下的热力学和电输运性质来解决SI转变的基本物理性质。研究和教育是通过博士的培训整合在他的计划。学生在物理以及提供研究经验，为年轻的学生。所研究的一些构型在电子技术中可能是重要的。