High Precision Landau Quantum Oscillation Measurements in the Normal and Mixed States of High-Temperature Superconductors

在这个项目中，测量了高温超导体在正常状态和超导混合状态下的朗道量子振荡。研究了钇钡氧化铜和铋锶稀土氧化铜的外延膜，以及其他超导体的块状单晶。所研究的物理包括费米表面拓扑结构、有效质量和正常状态下电子的散射率；混合状态下正常电子与磁涡流的相互作用以及高温超导材料在强朗道量子化正态背景下的超导性能。正常状态下的费米表面测量将给出对这些材料的超导机制理论至关重要的参数值。混合态的结果将大大改善电子-电子和电子-通量涡旋相互作用的描述。限制开发真正具有高温超导性（高于液氮温度-196摄氏度）的材料的问题之一是，产生高温超导性的基本机制仍然未知。目前的工作是通过测量参与超导的电子的基本性质，在超导和正常（电阻）条件下，在各种高温超导体中获得有关这种机制的信息。通过使用强磁场和测量电子的量子化磁性，获得了对超导理论至关重要的参数的精确值。这些信息可以用来定量地评估和测试这些理论。这些测量是使用美国国家强磁场实验室、路易斯安那州立大学和橡树岭国家实验室的专门设备进行的。＊＊＊

9501419 Goodrich In this project, measurements of Landau quantum oscillations are made on high temperature superconductors in both the normal and the superconducting mixed states. Both epitaxial films of yttrium barium copper oxide and bismuth strontium rare-earth copper oxide, and bulk single crystals of other superconductors are studied. The physics investigated includes Fermi surface topologies, effective masses, and scattering rates for electrons in the normal state; the interaction of normal electrons with flux vortices in the mixed state; and the behavior of superconducting properties of high temperature superconducting materials in the presence of a strongly Landau- quantized normal-state background. The Fermi surface measurements in the normal state will give values for parameters that are crucial to theories of the mechanism of superconductivity in these materials. The mixed state results will lead to a much improved description of electron-electron and electron-flux vortex interactions. %%% One of the problems limiting the development of materials that exhibit truly high-temperature superconductivity (above the temperature of liquid nitrogen, -196 deg C) is that the basic mechanism responsible for high-temperature superconductivity remains unknown. The present work is directed toward gaining information about this mechanism in a variety of high-temperature superconductors by measuring fundamental properties of the electrons that participate in superconductivity, in both the super-conducting and normal (resistive) condition. By using strong magnetic fields and measuring the quantized magnetism of the electrons, precise values are obtained for parameters that are crucial to theories of superconductivity. This information can then be used to evaluate and test quantitatively these theories. The measurements are made using specialized facilities at the National High Magnetic Field Labo ratory, at Louisiana State University, and at Oak Ridge National Laboratory. ***