Manipulating 2D Superconductivity through atomic scale control of boundary conditions

摘要：本课题旨在将超导体薄膜的性质控制在仅几个原子单层的范围内，并研究这种新体制下的超导性质。超导体薄膜在如此薄的状态下很可能表现出在大块形式中所没有的特性。例如，这样的薄膜可能能够在非常高的磁场存在下携带超电流，使薄膜对器件应用更有用。研究活动涉及最先进的合成技术，可以铺设薄膜原子层，从而使我们能够在微观尺度上实现最终的材料控制。此外，我们将利用表征工具研究从纳米到宏观（毫米）长度尺度的超导特性。该提案侧重于研究与教育的整合，以培养具有国际竞争力的材料研究学生。我们还致力于向各级更广泛的受众进行教育宣传。在UT-Austin， PI将利用以前在IGERT项目下建立的面向全州高中教师和学生的纳米科学和纳米技术夏季学院。此外，我们将通过“爱丽丝梦游仙境”项目为女高中生提供暑期实习机会；PI已经接待了其中四名学生作为暑期实习生，并将在未来几年继续这样做。最后，这个项目完全致力于扩大代表性不足的群体在研究生研究中的参与，具体目标是提高女性或/和西班牙裔研究生的比例。技术摘要：尺寸小、制作精美的功能材料是现代材料研究的核心。在过去的NSF-FRG项目的支持下，PI一直专注于精确定制的金属薄膜和量子体制下相关纳米结构的新物理特性。这些过去的努力在这种结构的生长和表征方面大大推动了该领域的发展。在拟议的计划中，我们将通过基于这些量子薄膜创建新的异质结构来实现另一个飞跃，以探索和利用其新兴的奇异超导特性，以实现潜在的应用。具体而言，我们将重点研究超导性与三种不同量子自由度（包括电子、晶格和自旋）的相互作用，并将实现以下四个主要任务领域：(a)将微观和宏观测量相关联-操纵结构缺陷并研究它们在相位波动中的作用；(b)重新探讨超导超薄膜的量子尺寸效应，揭示声子的量子约束；(c)界面工程调整原子层超导膜的超导性；(d)超薄外延薄膜中超导-自旋顺磁（SC-SP）转变的探索。

NON-TECHNICAL ABSTRACT:This proposal is aimed at controlling the properties of thin superconductor films in the range of only a few atomic monolayers and studying the superconducting properties in this new regime. The superconducting films in such a thin regime are likely to exhibit properties that are not found in the bulk form. For example, such a thin film may be able to carry supercurrent in the presence of very high magnetic fields making the film much more useful for device applications. The research activities involve state-of-the-art synthesis techniques that can lay down the thin film atomic layer by atomic layer thus enabling us to achieve the ultimate material control at the microscopic scale. In addition, we will use characterization tools to study the superconducting properties from nanometer to macroscopic (millimeter) length scales. The proposal focuses on the integration of research and education to train internationally competitive students in materials research. We are also committed to educational outreach to broader audiences at all levels. At UT-Austin the PI will take advantage of the Summer Academy of Nanoscience and Nanotechnology for state-wide high school teachers and students, previously established under the IGERT program. Moreover, we will offer summer internship opportunities for female high school students through the Alice in the Wonderland program; the PI has already hosted four of these students as summer interns and will continue to do so in future years. Finally, this program is fully committed to broadening participation of under-represented groups in graduate research with specific goals of increasing the percentage of graduate students that are women or/and of Hispanic background. TECHNICAL ABSTRACT:Elegantly fabricated functional materials with reduced dimensions occupy a central stage of modern materials research. Supported by an NSF-FRG program in the past, the PI has been focusing on the novel physical properties of precisely tailored metallic thin films and related nanostructures in the quantum regime. These past efforts have substantially advanced the field in terms of growth and characterization of such structures. In the proposed program, we will take another leap forward by creating new heterostructures based on these quantum films to explore and harness their emergent exotic superconducting properties for potential applications. Specifically, we will focus on the interplay of superconductivity with three different quantum degrees of freedom, including electronic, lattice, and spin, and we will implement the following four major task areas: (a) Correlating microscopic and macroscopic measurements - manipulating structural defects and investigating their roles on phase fluctuations; (b) Revisiting quantum size effect on superconductivity ultra-thin films and unraveling the quantum confinement of phonons; (c) Tuning superconductivity of atomic-layer superconducting films with interfacial engineering; and (d) Exploring superconducting - spin-paramagnetic (SC-SP) transition in ultra-thin epitaxial films.