Phase Coherence and Dynamics in Superconductor Arrays and Unconventional Superconductors

本实验研究项目的重点是远距离相相干在超导材料和器件中的作用。这项工作是基于PI开发的SQUID干涉测量技术来检测单晶超导体样品中的有序参数的相位；以及扫描SQUID显微镜（SSM）的使用。建议研究的三个领域包括：(1)利用SSM研究超导体阵列中的涡旋结构和动力学。(2)应用SQUID干涉测量方法识别重费米子超导体和有机超导体的序参量对称性，这两种材料都表现出非常规配对的迹象。(3)由d波和s波岛交替阵列等组成的混合系统的磁成像。这个实验研究项目处于非常规超导研究的前沿，主要研究超导体和超流体的“相相干”特性。超导体最有用的特性：超流体（无损）导电、超导量子干涉器件（SQUID）磁场传感器和快速逻辑元件，都是由相相干性产生的。最近人们很有可能发现，高Tc铜超导体的相参特性与传统超导体（如铅和NbTi）有显著不同。该研究项目部分致力于研究其他超导体、有机金属和“重费米子”超导体的相特性，这些超导体也可能表现出非常规的相行为。这项研究的一部分将使用扫描鱿鱼显微镜，它可以测量十亿分之一奥斯特（1/2奥斯特大约是地球磁场的水平）的局部磁场，空间分辨率约为100微米。这项研究的结果可能包括不同寻常的新效果或结构，可能会在技术上得到应用。这个研究项目是跨学科的，涉及研究生，他们将接受良好的培训，进入工业、政府或教育部门。＊＊＊

w:\awards\awards96\num.doc 9705695 Van Harlingen This experimental research project focuses on the role of long- range phase coherence in superconductor materials and devices. The work is based on the SQUID interferometry techniques the PI has developed to detect the phase of the order parameter in single crystal superconductor samples; and on the use of a scanning SQUID microscope (SSM). Three areas of proposed research include: (1) Use of the SSM to study vortex configurations and dynamics in superconductor arrays. (2) Application of the SQUID interferometry methods to identify the order parameter symmetry in heavy fermion superconductors and in organic superconductors, both types of material showing indications of unconventional pairing. (3) Magnetic imaging of hybrid systems consisting, e.g.,of alternating arrays of d-wave and s-wave islands. %%% This experimental research project, at the forefront of research in unconventional types of superconductivity, focuses on the "phase coherence" property of superconductors and superfluids in general. The most useful properties of superconductors: the superfluid (lossless) electrical conduction, and the Superconducting Quantum Interference Device (SQUID) magnetic field sensors and fast logic elements, all arise from phase coherence. It has recently been found with high probability that the phase-coherent properties of the high Tc cuprate superconductors are strikingly different from those of conventional superconductors, like lead and NbTi. This research project is devoted in part to the phase properties of additional types of superconductors, organic metals and "heavy fermion" superconductors, which may also exhibit unconventional phase behavior. Portions of this research will utilize a Scanning Squid Microscope, which can measure local m agnetic fields at the level of one billionth of an Oersted (1/2 Oersted is about the level of the earth's magnetic field) with a spatial resolution of about 100 micrometers. Results from this research may include unusual new effects or structures which may find application in technology. This research project is interdisciplinary in nature and involves graduate students who will be excellently trained to enter positions in industry, government or education. ***