Effects of Intrinsic and Disorder-Induced Anisotropies on the Vortex Dynamics and Superconducting Gap of High-Temperature Superconductors-From Macroscopic to Microscopic Scales

w：\awards\awards96\num.doc 9705171叶 该实验研究项目的重点是涡流动力学， 各向异性铜氧化物的涡旋钉扎 超导体，强调广泛的长度和激发频率尺度。 本论文的两个目标是研究不同静态无序下铜氧化物晶体和薄膜的本征各向异性和无序诱导各向异性对涡旋钉扎和动力学的竞争;以及从宏观到微观研究热诱导和电流驱动的涡旋动力学。 实验包括霍尔电导率的测量， 到 10 MHz;第一和第三谐波交流 磁化率从0.1Hz到0.1MHz，微波磁阻抗从6到26 GHz，使用高Q值的负载微波空穴。还将进行扫描隧道显微镜测量。 该实验研究项目的中心是磁场对铜氧化物高温超导体的影响，这些高温超导体在通信系统的滤波器和电力传输的载流导线等潜在应用中非常重要。 研究的重点是磁通线穿透超导体时的稳定性，磁通线的运动类型以及如何通过提供所谓的钉扎中心来最大限度地减少这种运动。磁通线运动导致内部能量损失和加热，并且在大多数应用中对效率有害。在这个项目中的实验工具包括测量谐波产生， 交流磁场与这种样品的相互作用，以及涡旋的研究 使用扫描隧道显微镜的几何形状。 这项研究的结果可能包括不寻常的新效果或可能在技术中找到新应用的材料。 这个研究项目是跨学科的性质， 涉及研究生，他们将接受出色的培训，进入工业，政府或教育部门。 ***

w:\awards\awards96\num.doc 9705171 Yeh This experimental research project focuses on the vortex dynamics and vortex-pinning of anisotropic cuprate superconductors, emphasizing a wide range of length- and excitation-frequency scales. Two goals of the work are to investigate competition between the intrinsic and disorder-induced anisotropies on the vortex pinning and dynamics of cuprate crystals and films with different static disorder; and to study the thermally-induced and current-driven vortex dynamics from macroscopic to microscopic scales. Experiments include measurement of the Hall conductivity up to 10MHz; the first- and third-harmonic ac magnetic susceptibility from 0.1Hz to 0.1MHz, and the microwave magneto- impedance from 6 to 26 GHz using high-Q sapphire-loaded microwave cativites. Scanning tunneling microscope measurements will also be made. %%% This experimental research project is centered on the effects of magnetic field on the cuprate high temperature superconductors, which are important in potential applications such as filters for communication systems and current carrying wires for power transmission. The research focuses on the stability of the magnetic flux lines as they penetrate the superconductor, the types of motions of the flux lines and how to minimize such motions by providing so-called pinning centers. Flux line motions lead to internal energy loss and heating and are detrimental to efficiency in most applications. The experimental tools in this project include measurement of harmonic generation in the interaction of ac magnetic fields with such samples, and study of vortex geometries using the scanning tunneling microscope. Results from this research may include unusual new effects or materials which may find new 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. ***