Tunneling and Transport in Ordered and Disordered Superconductors

该计划的主要焦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。这种转变在零温度下发生，以响应系统外部参数的调整，从而改变其量子力学基态。它们是通过在非零温度下测量受与相变相关的量子涨落影响的性质来研究的。虽然许多系统都存在QPTs，包括二维电子气，以及包括高温超导体在内的强关联电子材料，但SI相变是最基本的，因为它与量子力学的相数不确定性关系有关。SI转变的物理性质已经变得不确定，因为在一些工作中，已经出现了分离超导和绝缘基态的中间金属制度的证据。该计划的目标是通过仔细测量薄膜在超低温下的热力学和电传输特性来解决潜在物理性质的问题。该项目通过博士生的培养以及本科生和高中生的研究经验，将研究和教育融为一体。所研究的一些样本结构具有潜在的技术意义。这个项目的主要重点是研究金属超薄膜中的超导体-绝缘体(SI)转变。这种相变是量子相变(QPT)。与受温度调节的普通相变不同，QPTs是由外部参数(如磁场或电荷密度)调节的，并在绝对零度下发现。它们是通过在非零但低温下的测量来研究的，这些特性受温度和调谐参数值的接近程度的影响。其他展示QPTs的系统包括二维电子气和相关的电子材料，包括高温超导体。SI跃迁是量子物理中最基本的量子理论之一，因为它与量子物理的测不准原理有关。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。通过对物理学博士生的培训，以及为年轻学生提供研究经验，研究和教育被整合到他的项目中。所研究的一些配置在电子技术中可能很重要。

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.