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.

虽然多年来成功地解释了“经典”的相变，但有限温度，混乱和耗散的影响是在将相同方法应用于量子相变（QPT），尤其是在低维材料中的QPT时谨慎行事的几个原因。二维QPT的一个重要原型系统是薄膜中的超导体 - 绝缘体转变（SIT），上述所有效果都起着重要作用。 该项目将通过使用无定形的Inox膜来扩展SIT上的早期工作，并精心制造，以避免颗粒状效应，以探索与耗散和混乱效应有关的问题。在此类材料中，幅度波动变得重要，从而影响整体SIT行为。要研究的重要效果包括在存在耗散的情况下位于SIT的相图； SIT系统的电子微观结构在过渡附近和寻找电子相分离；可能的耗散来源；低场超导体金属过渡；以及绝缘阶段的性质及其起步超导行为。 除了在许多凝聚态物理学领域（包括了解高-TC超导体）的项目的重要智力内容外，它还将作为PI教授的新研究生级课程的基础，并通过拟议项目的概念和结果向学生介绍QPT。 参加该研究项目的学生将学习技能，使他们能够为学术界，行业或国家实验室的未来职业提供能力。%% %%未来设备将越来越多地依赖于计算机和其他电子系统的核心。 例如，将构建未来量子计算机的量子依赖于更改系统中的外部参数的能力，该参数诱导了从一个量子基态到另一个量子基态的过渡。 当此量子由宏观系统表示（例如，磁矩的宏观样本）时，从一个量子状态到另一个量子的过渡代表量子相变（QPT）。 理解QPT对于一般凝结物质系统也至关重要，因为在低温下，它几乎在每个量子系统中都显示出来。 耗散和混乱的影响预计是对设备的限制效应，同时构成了对QPT的理论理解的挑战。 薄膜中的超导体 - 绝缘体转变（SIT）是在存在这些限制效应的情况下QPT的模型系统。 能够很好地控制其电子特性和混乱的薄膜的能力为回答QPT物理和未来量子设备物理学的许多开放问题提供了独特的机会。 从事该项目的研究生将学习技能，使他们能够从事未来的科学或技术职业。 科学和流行的出版物以及PI将在该主题上教授的新课程将是传达该项目结果的主要场所。