Theoretical Study on Novel Physical Properties of Nano-scale Exotic Superconductors

纳米级奇异超导体新物理性质的理论研究

基本信息

批准号：
18510090
负责人：
EBISAWA Hiromichi
金额：
$ 2.66万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2006
资助国家：
日本
起止时间：
2006 至 2007
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-18510090/
关键词：
exotic superconductor high Tc superconductor multiple Josephson junction scanning SQUID microscope topological crystals phase defects nano-scale superconductor noise reduction 多重ジョゼフソン効果ナノ超伝導超伝導ゆらぎ

项目摘要

Aiming to develop a frontier of novel physics in nano-scale exotic superconductors, several studies have been advanced.(1) Numerical studies on multiple Josephson junctions in d-wave high-Tc superconductors: By numerically solving differential equations describing the time evolution of the phase differences, we have observed that the localized oscillation modes, which correspond to the breather modes in sine-Gordon equation, causes a non-zero voltage in superconducting state, thus driving the transition to resistive state. These modes actually work as "seeds" inducing the transition.(2) A procedure to improve the resolution of the images of scanning SQUID microscope is studied, which is useful in observing the magnetic field distribution in d-wave/s-wave (or p-wave/s-wave) hybrid superconducting systems. In order to minimize the effects of noise and finite coil size, numerical simulation is advanced and comparison with experiments is made. The difficulty in application to images with non-zero magnetic field near the edges has been overcome with the help of the simulations.(3) To exemplify of the effects of sample geometry, we have studied the distribution of dislocations in tiny ring-shaped crystals and found several different dislocation distributions. To be more precise, ring-shaped topological crystals of NbSe3 etc. are studied within linear elastic theory. The uniform distribution of dislocations in crystals with circumferences larger than 1 micron is predicted. Below this size, the destruction of elastic coupling can take place.(4) The effects of superconducting fluctuations in the conductivity of tiny superconducting networks are studied. Under an AC current noise, a Shapiro-step-like structure appears in the current-voltage characteristics of current-biased system, causing an anomalous nonlinear resistivity.

为了在纳米级外来超导体中开发新型物理学的前沿，进行了几项研究。（1）关于D-Wave高-TC超导体中多个Josephson连接的数值研究：通过数值求解微分方程，描述了描述差分方程相位差异，我们已经观察到，与正弦 - 戈登方程中的呼吸模式相对应的局部振荡模式会在超导状态下导致非零电压，从而推动过渡到电阻状态。这些模式实际上是诱导过渡的“种子”。（2）研究了一种改善扫描鱿鱼显微镜图像分辨率的程序，这对于观察D-WAVE/S-WAVE中的磁场分布非常有用（或P-波/S波）混合超导系统。为了最大程度地减少噪声和有限线圈大小的影响，要进行数值模拟，并与实验进行了比较。在模拟的帮助下，已经克服了边缘附近非零磁场的图像的难度。（3）为了示例样品几何形状的影响，我们研究了微小环形晶体中位错的分布并发现了几个不同的错位分布。更确切地说，在线性弹性理论中研究了NBSE3等的环形拓扑晶体。预测圆周大于1微米的晶体中位错的均匀分布。低于此大小，可以进行弹性耦合的破坏。（4）研究了微型超导网络电导率中超导波动的影响。在交流电流噪声下，shapiro-step样结构出现在电流偏置系统的电流特征中，导致异常的非线性电阻率。