Institute for Superconducting and Electronic Materials, University of Wollongong, Northfields Avenue, Wollongong, NSW 2522, Australia.
National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), 31 Kashirskoye Shosse, 115409, Moscow, Russian Federation.
Sci Rep. 2017 Jan 9;7:40235. doi: 10.1038/srep40235.
The dynamics of transient current distributions in superconducting YBaCuO thin films were investigated during and immediately following an external field ramp, using high-speed (real-time) Magneto-Optical Imaging and calculation of dynamic current profiles. A number of qualitatively unique and previously unobserved features are seen in this novel analysis of the evolution of supercurrent during penetration. As magnetic field ramps up from zero, the dynamic current profile is characterized by strong peaks, the magnitude of which exceed the conventional critical current density (as determined from static current profiles). These peaks develop close to the sample edges, initially resembling screening currents but quickly growing in intensity as the external field increases. A discontinuity in field and current behaviour is newly observed, indicating a novel transition from increasing peak current toward relaxation behaviour. After this transition, the current peaks move toward the centre of the sample while reducing in intensity as magnetic vortices penetrate inward. This motion slows exponentially with time, with the current distribution in the long-time limit reducing to the expected Kim-model profile.
超导 YBaCuO 薄膜中瞬态电流分布的动力学特性在外部磁场斜坡期间和之后立即进行了研究，使用高速（实时）磁光成像和动态电流分布的计算。在对贯穿过程中超电流演化的这种新颖分析中，观察到了一些定性独特且以前未观察到的特征。随着磁场从零上升，动态电流分布的特征是强峰值，其幅度超过了传统的临界电流密度（从静态电流分布确定）。这些峰值在样品边缘附近发展，最初类似于屏蔽电流，但随着外磁场的增加，其强度迅速增加。观察到磁场和电流行为的不连续性，表明从电流峰值增加到弛豫行为的新型转变。在这个转变之后，电流峰值向样品中心移动，同时随着磁涡旋向内穿透而强度降低。这种运动随时间呈指数级减慢，在长时间极限下，电流分布减少到预期的 Kim 模型分布。
