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

9501419古德里奇在这个项目中，测量了高温超导体在正常态和超导混合态下的朗道量子振荡。研究了Y-BaO-CuO和铋-锶-稀土-铜氧化物的外延薄膜以及其他超导体的大块单晶。所研究的物理包括正常态电子的费米表面拓扑、有效质量和散射率；混合态中正常电子与磁通涡旋的相互作用；以及高温超导材料在强Landau量子化正常态背景下的超导性质的行为。正常状态下的费米面测量将给出参数的值，这些参数对于这些材料的超导机制的理论至关重要。混合态的结果将大大改善对电子-电子和电子通量-涡旋相互作用的描述。%限制真正表现出高温超导电性(高于液氮温度，-196℃)的材料发展的问题之一是，导致高温超导电性的基本机制尚不清楚。目前的工作旨在通过测量在超导和正常(电阻)条件下参与超导的电子的基本性质来获得关于各种高温超导体中这一机制的信息。通过使用强磁场和测量电子的量子化磁性，可以获得对超导理论至关重要的参数的精确值。然后，这些信息可以用来评估和定量测试这些理论。测量是使用路易斯安那州立大学国家高磁场实验室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. ***