Spin fluctuations and Magnetic Field Enhanced Superconductivity in two-dimensional localized system

二维局域系统中的自旋涨落与磁场增强超导

基本信息

批准号：
10640343
负责人：
SUZUKI Takao
金额：
$ 2.18万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10640343/
关键词：
Superconductivity Amorphous film Tc-enhancement AuGe film Au-Ge合金膜

项目摘要

We obtained the following results for the competitive effect of spin paramagnetic effect on superconductivity and localization in two-dimensional thin Au-Ge films.(1) Tc-enhancement under parallel magnetic fields is confirmed from the observations of the decrease in resistances in resistive transitions for thin films of AuィイD20.5ィエD2GeィイD20.5ィエD2 in thickness region of about 2nm. For those of AuィイD20.3ィエD2GeィイD20.7ィエD2 and AuィイD20.7ィエD2GeィイD20.3ィエD2, no Tc-enhancement is observed.(2) In field-sweep and -modulation experiments on resistive transition, the low field behavior below lkG is found to be different from those expected from the steady state experiments in (1) due to the vortex dynamics in staggered fields.(3) Typical temperature dependence and the nonlinear behavior are not obsereved because the external fields are not completely excluded. At the lowest temperature of T/Tco=0.7, resistance appears linearly with increasing applied perpendicular field H and its temperature dependence is consistent with the vortex flow resistivity due to thermal excitation. This implies that the vortex-glass transition is absent in two dimensional system.(4) Resistive transitions are investigated under exactly parallel fields by using a Hermholtz magnet to compensate the residual perpendicular fields. Positive magnetoresistances due to localization are quadratically proportional to H// and the superconducting resistive transitions are scaled by T/Tc(H//). The Tc-enhancement evaluated from the field dependence of resistance agree with those obtained in steady field experiments in (1).

对于二维Au-Ge薄膜中自旋顺磁效应对超导性和局域化的竞争效应，我们得到了以下结果。（1）平行磁场下Tc的增强通过电阻转变中电阻下降的观察得到证实。对于厚度约为 2nm 的 AuD20.5D2GeD20.5D2 薄膜。 AuD20.3D2GeD20.7D2和AuD20.7D2GeD20.3D2，没有观察到Tc增强。(2)在电阻转变的场扫描和调制实验中，发现lkG以下的低场行为与预期的不同。由于涡流动力学交错，导致（1）中的稳态实验(3) 由于未完全排除外部场，因此未观察到典型的温度依赖性和非线性行为。在 T/Tco=0.7 的最低温度下，电阻随施加的垂直场 H 的增加呈线性关系，并且其温度依赖性是一致的。与热激发引起的涡流电阻率的关系，这意味着二维系统中不存在涡流-玻璃转变。(4) 使用赫姆霍兹在完全平行的场下研究电阻转变。由于局部化而产生的正磁阻与 H// 成二次方，并且超导电阻转变由 T/Tc(H//) 缩放，根据电阻的场依赖性评估的 Tc 增强与那些在（1）中的稳定现场实验中获得的。