Superconductor-Insulator Transitions of Ultra-thin Films

* 技术摘要 * 本计划将研究元素和简单化合物的超导体-绝缘体转变（SIT）。这些跃迁是连续量子相变的最简单例子，它们发生在零温度下，当系统的基态响应于外部参数的变化而改变时。量子相变是量子力学的宏观表现，通过测量在低温但非零温度下持续存在的量子涨落影响的行为来研究。 调查将包括跨磁场调谐过渡的能斯特效应的研究，以及在临界区域中的穿透深度的测量，其目标是确定序参数和普适性类的临界指数。 此外，临界点附近的电子可压缩性，这将是一个热力学签名的SI转变，和耗散调谐的SI转变将进行研究。双电层晶体管配置将用于修改FeSe薄膜的电子和超导性质。更广泛的影响包括在传统的物理学博士课程中培养研究生。计划，并为本科生提供有用和积极的研究经验的场所。这项工作将影响对已知新型超导体的理解和对新超导体的探索。 主要的外展活动将是由PI教授关于物理主题的新生研讨会。* 非技术摘要 * 该奖项支持对元素和简单化合物的超导体-绝缘体转变的研究。超导体-绝缘体转变是最简单的量子相变之一，由于它们与量子力学的不确定性原理有关，因此它们特别重要。量子相变是当代凝聚态科学的一个重要范式，理解它们的性质是一个重要的挑战，部分原因是它们在高温超导中的作用。 量子相变，与传统的热力学相变，这是由温度控制，并发生在非零温度，是过渡，这是由外部参数，如磁场，压力，或电荷密度控制，并发生在绝对零度。 它们在低温但非零温度下具有可测量的特征，这将用于表征它们。超导体-绝缘体转变的研究需要先进的实验科学工具，如纳米纤维、薄膜生长和超低温低温测量技术。该项目支持培养博士和博士生。和本科生，这是一个很好的科学生涯的准备。主要的外展活动将是由PI在当代物理主题上教授新生研讨会。

****Technical Abstract****This program will investigate superconductor-insulator transitions (SITs) of ultrathin films of elements and simple compounds. These transitions are the simplest examples of continuous quantum phase transitions, which occur at zero temperature, when the ground state of a system is changed in response to the variation of an external parameter. Quantum phase transitions, which are macroscopic manifestations of quantum mechanics, are studied through measurements of behaviors influenced by quantum fluctuations that persist at low, but nonzero temperatures. Investigations will include a study of the Nernst effect across the magnetic-field-tuned transition, and measurements of the penetration depth in the critical region with the goal of identifying the critical exponent of the order parameter and the universality class. In addition, the electronic compressibility near the critical point, which would be a thermodynamic signature of the SI transition, and the dissipation-tuned-SI-transition will be investigated. Electric double layer transistor configurations will be used to modify the electronic and superconducting properties of FeSe films. The broader impacts include training of graduate students in a traditional physics Ph.D. program and providing a venue for useful and positive research experiences for undergraduates. The work proposed will impact the understanding of known novel superconductors and the search for new ones. The primary outreach activity will be the teaching of freshman seminars by the PI on physics topics. ****Non-Technical Abstract****This award supports investigations of the superconductor-insulator transitions of elements and simple compounds. Superconductor-insulator transitions are among the simplest quantum phase transitions, and they are especially fundamental because of their connection to the Uncertainty Principle of quantum mechanics. Quantum phase transitions are an important paradigm in contemporary condensed matter science and understanding their nature is an important challenge in part because of their role in high temperature superconductivity. Quantum phase transitions, in contrast with conventional thermodynamic phase transitions, which are controlled by temperature, and occur at nonzero temperature, are transitions, which are controlled by external parameters such as magnetic field, pressure, or charge density, and occur at absolute zero. They have measurable signatures at low, but nonzero temperatures, which will be used to characterize them. The study of superconductor-insulator transitions requires advanced tools of experimental science such as nanofabrication, thin film growth, and ultra-low temperature cryogenic measurement techniques. This project supports the training of both Ph.D. and undergraduate students that is excellent preparation for a scientific career. The primary outreach activity will be the teaching of freshman seminars by the PI on contemporary physics topics.