Studies of Two-Dimensional Superconductors and Multilayers in Magnetic Fields

为了更好地了解全球温度与磁场相图，以及与二维和层状超导体（如高温超导体）的各种相相关的动力学，将进行广泛的实验。研究了平均场线附近超导跃迁的热力学，以及各向异性多层材料的最低朗道-勒特近似的有效范围。在二维涡旋晶格的熔化实验中，随着长度尺度的调整，将重点关注涡旋动力学中的不同交叉。超导体-绝缘体跃迁将通过系统地改变屏蔽度和库仑势来研究。随着无序量的增加，零场超流体跃迁的性质也将被研究。通过研究无序对阻力跃迁和涡旋动力学的影响，可以理清弱钉和强钉的区别。上述实验中的各种输运和磁测量将提供多层的整体相图，这可能会揭示新的玻璃相及其早期相关性。高温超导体是层状材料，其超导性发生在铜-氧平面上。由于这种二维性，它们表现出特殊的性质。本文研究了高温超导体和二维超导体在磁场中的电阻跃迁，以及涡旋结构和运动引起能量耗散的作用。广泛的实验将在钼锗/锗多层模型系统上进行，其中PI具有广泛的专业知识和控制和表征能力。这些实验一起将提供一个更好的理解相图以及动力学与二维和层状超导体的各种相。＊＊＊

9508419 Kapitulnik A wide range of experiments will be conducted in order to obtain a better understanding of the global Temperature vs. Magnetic field phase diagram, as well as the kinetics associated with various phases of two dimensional and layered superconductors such as the high-temperature superconductors. The thermodynamics of the superconducting transition near the mean-field line, and the range of validity of the Lowest-Landau-Letel approximation to multilayers with various anisotropy will be investigated. Experiments on the melting of the two-dimensional vortex lattice will focus on different crossovers in the vortex dynamics as the length scales are being tuned. Superconductor-insulator transitions will be studied by varying systematically the degrees of screening and the Coulomb potential. The nature of the zero-field superfluid transition with increasing amount of disorder will also be investigated. The difference between weak and strong pinning will be sorted out by studying the role of disorder on the resistive transition and vortex dynamics. The variety of transport and magnetic measurements in the above experiments will provide the global phase diagram of the multilayers, this may uncover new glass phases and their incipient correlation. %%% High temperature superconductors are layered materials where superconductivity occurs in the copper-oxygen planes. They exhibit peculiar properties due to this two-dimensionality. This proposal investigates the resistive transition in magnetic fields, and the role of vortex structure and motion causing energy dissipation in high temperature superconductors and two dimensional superconductors in general. A broad range of experiments will be conducted on a model system of molybdenum-germanium/germanium multilayer in which the PI's have extensive expertise and capabilities of co ntrol and characterization. These experiments together will provide a better understanding of the phase diagram as well as the kinetics associated with the various phases of two-dimensional and layered superconductors. ***