Superconductors, Insulators, Metals and Quantum Phase Transitions in Two-Dimensional Films

二维薄膜中的超导体、绝缘体、金属和量子相变

• 批准号: 0406339
• 负责人: Aharon Kapitulnik
• 金额: $ 42.5万
• 依托单位: Stanford University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-11-01 至 2009-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0406339&HistoricalAwards=false
• 关键词: Superconductors; Insulators; Metals; Quantum; Phase

While "classical" phase transitions have been explained successfully for many years, the effects of finite temperature, disorder, and dissipation are several reasons to exercise caution when applying the same approach to quantum phase transitions (QPT), and in particular QPT in low-dimensional materials. An important prototype system for 2-dimensional QPT is the superconductor-insulator transition (SIT) in thin films where all the above effects play an important role. This project will extend earlier work on the SIT by using amorphous InOx films, carefully fabricated to avoid granular effects to explore issues related to dissipation and disorder effects. In such materials amplitude fluctuations become important and thus affect the overall SIT behavior. Important effects to be studied include the phase diagram of the SIT in the presence of dissipation; the electronic microstructure of SIT system near the transition and the search for electronic phase separation; the possible sources of dissipation; the low-field superconductor-metal transition; and the nature of the insulating phase, and its incipient superconducting behavior. Besides the important intellectual content of the project that bears on many areas of condensed matter physics, including the understanding of high-Tc superconductors, it will also serve as a basis for a new graduate level course that will be taught by the PI, introducing QPT to the students through concepts and results of the proposed project. The students participating in this research project will learn skills that will equip them for future careers in academia, industry, or national laboratories.%%%Future devices that will be in the heart of computers and other electronic systems are increasingly expected to depend on quantum mechanics. For example a qubit that will build a future quantum computer relies on the ability to change an external parameter in the system that induces a transition from one quantum ground state to another. When this qubit is represented by a macroscopic system (e.g. a macroscopic sample of magnetic moments), a transition from one quantum state to another represents a quantum phase transition (QPT). Understanding QPT is also of chief importance for general condensed matter systems as it appears in almost every quantum system at low temperatures. Effects of dissipation and disorder are expected to be limiting effects for devices and at the same time pose challenge for theoretical understanding of QPT. The superconductor-insulator transition (SIT) in thin-films is a model system for QPT in the presence of those limiting effects. The ability to fabricate films with good control of their electronic properties and disorder provides a unique opportunity to answer many of the open questions that bear on the physics of QPT and future quantum devices. Graduate students working on the project will learn skills that will equip them for future scientific or technological careers. Scientific and popular publications, as well as a new course that will be taught by the PI on the subject will be the main venue to communicate the results of this project.

虽然“经典”相变多年来已被成功解释，但有限温度、无序和耗散的影响是在将相同方法应用于量子相变（QPT）时要谨慎的几个原因，特别是低量子相变中的 QPT。维度材料。二维 QPT 的一个重要原型系统是薄膜中的超导-绝缘体转变 (SIT)，其中所有上述效应都发挥着重要作用。 该项目将通过使用精心制作的非晶 InOx 薄膜来扩展 SIT 的早期工作，以避免颗粒效应，从而探索与耗散和无序效应相关的问题。在此类材料中，振幅波动变得很重要，从而影响整体 SIT 行为。要研究的重要影响包括存在耗散时 SIT 的相图； SIT体系近跃迁的电子显微结构及电子相分离的探索；可能的耗散来源；低场超导-金属转变；以及绝缘相的性质及其初期的超导行为。 除了该项目涉及凝聚态物理许多领域（包括对高温超导体的理解）的重要知识内容外，它还将作为 PI 教授的新研究生课程的基础，介绍 QPT通过拟议项目的概念和结果向学生展示。 参与该研究项目的学生将学习技能，为他们未来在学术界、工业界或国家实验室的职业生涯做好准备。%%%未来将成为计算机和其他电子系统核心的设备越来越多地依赖于量子机械师。 例如，构建未来量子计算机的量子位依赖于改变系统中外部参数的能力，从而导致从一种量子基态转变为另一种量子基态。 当该量子位由宏观系统（例如磁矩的宏观样本）表示时，从一种量子态到另一种量子态的转变表示量子相变（QPT）。 了解 QPT 对于一般凝聚态物质系统也至关重要，因为它几乎出现在每个低温量子系统中。 耗散和无序的影响预计将限制器件的影响，同时对 QPT 的理论理解提出挑战。 薄膜中的超导-绝缘体转变 (SIT) 是存在这些限制效应时 QPT 的模型系统。 制造能够良好控制其电子特性和无序性的薄膜的能力提供了一个独特的机会来回答与 QPT 和未来量子器件的物理相关的许多悬而未决的问题。 从事该项目的研究生将学习技能，为他们未来的科学或技术职业做好准备。 科学和流行出版物以及 PI 将教授的有关该主题的新课程将成为交流该项目成果的主要场所。