Probing and manipulating strained interfaces with oxide superconductors

非技术描述：超导体能够无损耗地传输电流，这是自然界中最奇特的物理现象之一。这种能力用临界电流密度Jc，超导性来定量描述。增强型Jc将为恢复电网的可靠性、提高其容量和效率提供强大的新机遇，这被视为一项工程上的重大挑战。随着能源需求的增加和现有电网的老化，美国将面临提供丰富、可靠的清洁能源以满足国家未来生产力、经济增长和生活质量的危机。氧化物高温超导体（HTSs）的发现使超导体在液氮温度下的应用成为可能，但由于其不同寻常的物理性质，对Jc产生了深远的影响，也成为一个迷人的研究课题。在过去的二十年里，提高高温超导材料的Jc一直是世界范围内应用超导领域的研究热点。特别是，一个长期存在的问题是，在实际的高温超导导体中，通过以纳米级精度精确控制材料微结构，是否可以达到理论预测的最大Jc（所谓的依赖极限）。纳米科学的最新进展为高温超导材料的微结构工程提供了新的机会。在这个项目中，通过在纳米尺度上控制电流来设计物理性能的方法代表了传统经验方法的飞跃，在传统经验方法中，高温超导材料的开发没有基础物理学的精确指导。这样的研究也为下一代在纳米科学和材料科学领域的教育提供了前沿。技术描述：以纳米级精度控制微观结构是实现具有非凡功能的材料的关键，由于缺乏对基础物理学的理解和在这种尺度上工程原子排列的方法，这一直是高温超导材料研究和其他技术上有趣的材料研究的主要挑战。一种综合建模-合成-表征方法被用于解决这一挑战，以理解、预测和操纵嵌入YBa2Cu3O7-d (YBCO) HTS膜中的人工钉钉中心（APCs）的功能纳米复合材料中的应变界面。目标是实现APC的可控自组装，并精确设计形态、取向、密度和控制APC/HTS接口，使其基于基本物理设计规则发挥最佳功能。提出了四个综合主题；所有的研究都集中在了解和控制界面应变，以实现高Jc APC/YBCO纳米复合材料的可控生长。主题1通过了解不同掺杂浓度和YBCO基质菌株的微观调控机制，重点研究了APCs线性排列的该构型相图。应变在相关界面上的作用将被量化。主题2研究了YBCO基体中线性APC的应变界面对APC/HTS纳米复合材料Jc的影响，并探讨了减少或消除该应变界面上氧无序对纳米复合材料薄膜超导性的不利影响的方法。主题3的重点是寻找直径更小，接近超导相干长度的线性apc，以及在非常高的磁场下具有更高Jc的高密度相关线性apc。主题4研究了纳米结构的自发自组装动力学。

NON-TECHNICAL DESCRIPTION: Superconductors are capable of carrying electric current without loss, one of the most exotic physical phenomena in nature. This capability is described quantitatively by critical current density Jc, superconductivity. Enhanced Jc will provide powerful new opportunities for restoring the reliability of the power grid and increasing both its capacity and efficiency, regarded as an engineering grand challenge. As energy demands increase and our existing grid ages, the USA will face a crisis situation to provide abundant, reliable clean energy power to meet the nation's future productivity, economic growth and quality of life. The discovery of oxide high temperature superconductors (HTSs) made superconductor applications possible at liquid nitrogen temperature, but also presented a fascinating research topic due to their unusual physical properties, resulting in profound effects on Jc. Raising Jc in HTSs has been the focus of world-wide efforts in the field of applied superconductivity during the past two decades. In particular, a long-standing question is whether the theoretically predicted maximum Jc (so-called depairing limit) can be reached in practical HTS conductors through precise control of material microstructures with nanoscale precision. Recent advances in nanoscience have provided fresh opportunities in engineering the microstructures of HTS materials. The approach undertaken in this project of designing physical properties via controlling the electric current at the nanoscale represents a leap forward from the traditionally empirical method in which the HTS materials have been developed without a precise guidance of fundamental physics. Such a research also provides the forefront of education for the next generation in the fields of nanoscience and material science.TECHNICAL DESCRIPTION: Controlling microstructure with nanoscale precision is the key to achieving materials with extraordinary functionality and has been a major challenge in material research of HTS and other technologically interesting materials due to lack of understanding of fundamental physics and approaches for engineering atomic arrangement at such a scale. An integrated modeling-synthesis-characterization approach is being used to address such a challenge to understand, predict and manipulate the strained interfaces in functional nanocomposites of artificial pinning centers (APCs) embedded in HTS films of YBa2Cu3O7-d (YBCO). The goal is to achieve controllable self-assembly of APCs with precisely designed morphology, orientation, density and controlled APC/HTS interfaces to function optimally based on the basic physics design rules. Four integrated themes are proposed; all are focused on understanding and manipulating interface strains towards controllable growth of APC/YBCO nanocomposites for high Jc. Theme 1 focuses on the study of this configuration's phase diagram with a linear arrangement of APCs through understanding the microscopic controlling mechanisms at different dopant concentrations and YBCO matrix strains. The role of strain on the relevant interfaces will be quantified. Theme 2 investigates the effect of strained interfaces of linear APCs in a YBCO matrix on the Jc of the APC/HTS nanocomposites and explores ways to reduce or eliminate the detrimental effect of the oxygen disorder at such a strained interface on superconductivity of the nanocomposites films. Theme 3 focuses on a search for linear APCs with smaller diameters that approach the superconducting coherence length as well as higher density, correlated linear APCs for higher Jc at very high magnetic fields. Theme 4 investigates the kinetics of the spontaneous self-assembly of nanostructures.