An Exponential Model for Critical Current Density Through a Low-Angle Grain Boundary in a High-T c Superconductor

Xue, Feng; Gou, Xiaofan

doi:10.1007/s10948-016-3608-x

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“…GB in type-II superconductors and the effect on vortex motion have been studied in various researches performed on thin films and bulk samples. [14][15][16][17][18][19][20][21][22] By means of magnetooptical and magnetic hysteresis measurements, GB in superconductors was found to play a strong obstructive barrier for vortex motion in most cases, and later studies further indicated that GB can also be an easy-flow channel of vortices under certain conditions. [23,24] Recently more researches focused on the dependence of the GB angle on vortex motion.…”

Section: Introductionmentioning

confidence: 99%

Barrier or easy-flow channel: The role of grain boundary acting on vortex motion in type-II superconductors*

Liu¹,

Gou²,

Xue³

2021

Chinese Phys. B

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Grain boundaries (GBs), as extremely anisotropic pinning defects, have a strong impact on vortex motion in type-II superconductors, and further on the macro level dominates the superconductivity for example the critical current density. Many previous studies indicated that mostly GB plays the role of a strong barrier for vortex motion, while an easy-flow channel just under some certain conditions. In order to thoroughly make clear of the questions of what is exactly the role of GB on vortex motion and how it works, in this article we developed a large scale molecular dynamic model and revealed the action of GB on vortex motion in type-II superconductors. The most significant finding is that the role of GB on vortex motion can be changeable from a barrier to an easy-flow channel, and which is intrinsically determined by the competition effect correlated with its action on vortex between in the GB and no-GB regions. Such the competition effect essentially depends on the attributes of both the GB (described by the GB strength and angle θ) and no-GB pining regions (by the relative disorder strength α p/α v). Specifically, for a YBa2Cu3O7 – x (YBCO) sample, to obtain a clear knowledge of vortex motion in GB region, we visualized the three typical trajectories of vortices during the three vortex movement stages. Further, in order to understand how GB results in the macro current-carrying property, corresponding to the current–voltage relation of the YBCO conductor, we obtained the average velocity vy of vortices varying with their driving force, which is nearly identical with the previous observations.

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