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.

该程序的主要重点是超薄膜中的超导体 - 绝缘体（SI）过渡，这是量子相变（QPT）的一个例子。此类过渡在零温度下发生，响应于改变其量子机械基态的系统的外部参数。通过与过渡相关的量子波动影响的非零温度的测量进行研究。尽管许多系统表现出QPT，包括二维电子气体以及包括高温超导体在内的强相关电子材料，但SI转变是最基本的，因为它与量子力学的相位数不确定性关系有关。 SI过渡物理学的性质已变得不确定，因为在某些工作证据中，分离超导和绝缘基态的中间金属政权已经出现。该程序的目的是通过仔细测量超低温度下膜的热力学和电运输特性来解决基础物理的性质。通过培训博士学位，研究和教育纳入了该计划。学生以及本科生和高中生的研究经验。研究的一些样本结构具有技术意义的潜力。 %%％这些程序的主要重点是对金属超薄膜中超导体 - 绝缘体（SI）过渡的研究。该过渡是量子相变（QPT）。与通过温度调整的普通相变相反，QPT由外部​​参数（例如磁场或电荷密度）调整，并且在绝对零下发现。通过非零的测量值（但低温）对它们进行了研究。展示QPT的其他系统包括二维电子气体和相关的电子材料，包括高温超导体。 SI过渡是QPT中最基本的转变之一，因为它与量子物理的不确定性原理有联系。该程序的目的是通过在超低温度下的热力学和电运输特性测量来解决SI转变的基本物理的性质。通过培训博士学位，研究和教育纳入了他的计划。物理学的学生以及为年轻学生提供研究经验。研究的一些配置在电子技术中可能很重要。