We investigated vortex dynamics in a single-crystal sample of type-II superconductor NbSe$_{2}$ using scanning tunneling microscopy at 4.2 K. The decay of the magnetic field at a few nT/s in our superconducting magnet induced the corresponding motion of vortices at a few pm/s. Starting with an initial magnetic field of 0.5 T, we continued to observe motion of vortices within a field of view of 400$\times$400 nm$^2$ subject to decay of the magnetic field over a week. Vortices moved collectively, and maintained triangular lattices due to strong vortex-vortex interactions during the motion. However, we observed two peculiar characteristics of vortex dynamics in this superconductor. First, the speed and direction of the vortex lattice motion were not uniform in time. Second, despite the non-uniform motion, we also found that there exists an energetically favored configuration of the moving vortices in the single-crystal sample of NbSe$_{2}$ based on the overlaid trajectories and their suppressed speeds. We model the system with weak bulk pinning, strong bulk pinning, and edge barrier effects.
Chiral superconductors from parent states with nonuniform Berry curvature: Momentum-space vortices, Bogoliubov-de Gennes topology, and thermal Hall conductivity
University of Toronto（多伦多大学）；Canadian Institute for Advanced Research（加拿大高等研究院）
Vortex deformation and breaking in superconductors: A microscopic description
传统上研究了非均匀临界电流密度下的涡旋破碎，尽管它也可能由于非均匀钉扎力分布而出现。在这篇文章中，我们研究的情况下，高钉扎/低钉扎/高钉扎分层结构。我们已经开发了一个弹性模型来描述在这些系统中的一个涡旋的变形在一个均匀的传输电流密度$J$的存在下，对于任何任意取向的传输电流和磁场。如果$J$高于某个临界值$J_c$，则涡流破裂，并出现有限的有效电阻。我们的模型可以应用到一些实验配置，涡破碎自然存在。对于$_2$ $_3$ O $_{7-x}$（YBCO）小角度晶界和相邻衬底上的膜，情况就是这样，其中分别由Abrikosov-Josephson涡旋（AJV）和Josephson弦涡旋（SV）经历断裂。与我们的模型，我们已经实验提取了一些内在的参数的AJV和SV，如线张力$ε_l$，并将其与现有的预测的基础上的涡结构。
Enhancement of critical current density in superconducting/magnetic multi-layers with slow magnetic relaxation dynamics and large magnetic susceptibility
Unconventional critical state in YBa$_{2}$Cu$_{3}$O$_{7-δ}$ thin films with a vortex-pin lattice fabricated by masked He$^+$ ion beam irradiation
在$_{2}$ $_{3}$ O $_{7-δ}$超导薄膜中，形成了由直径为180 nm、间距为300 nm的柱状缺陷区（CD）组成的涡旋钉扎晶格。它们是通过用75 keV He $^+$离子通过模板掩模辐照而制造的。临界电流的峰值揭示了在样品边缘附近的域中的涡旋的相称捕获。在斜坡的外部磁场，临界电流峰值的位置从它们的平衡值移动到较低的磁场中的处女和较高的磁场中的磁场饱和下扫曲线，分别。根据以前的理论预测，这种不可逆性被解释为一个不均匀的，梯田状的临界状态，其中个别域被占据的固定数量的涡钉扎网站。的磁阻，在低电流密度下探测，是滞后和角度依赖性，并表现出最小值，对应于临界电流的峰值。极小值的位置与平行于CD轴的磁场分量成比例，只要倾斜的涡旋可以容纳在CD内。这种行为，不同于未照射的薄膜，证实了CD主导的钉扎。
Trapping magnetic flux quanta in superconducting 3D caps
Technische Universität Braunschweig（布伦瑞克工业大学）；Leibniz IFW Dresden（德累斯顿莱布尼茨固体与材料研究所）；Moldova State University（摩尔多瓦国立大学）；FLUXONICS—The European Foundry for Superconducting Electronics e.V.（FLUXONICS——欧洲超导电子制造协会）
