Robinson Research Institute, Victoria University of Wellington, P.O. Box 33436, Lower Hutt, 5046, New Zealand.
MacDiarmid Institute for Advanced Materials and Nanotechnology, P.O. Box 33436, Lower Hutt, 5046, New Zealand.
Sci Rep. 2017 Aug 30;7(1):10010. doi: 10.1038/s41598-017-10226-z.
Universal scaling behaviour in superconductors has significantly elucidated fluctuation and phase transition phenomena in these materials. However, universal behaviour for the most practical property, the critical current, was not contemplated because prevailing models invoke nucleation and migration of flux vortices. Such migration depends critically on pinning, and the detailed microstructure naturally differs from one material to another, even within a single material. Through microstructural engineering there have been ongoing improvements in the field-dependent critical current, thus illustrating its non-universal behaviour. But here we demonstrate the universal size scaling of the self-field critical current for any superconductor, of any symmetry, geometry or band multiplicity. Key to our analysis is the huge range of sample dimensions, from single-atomic-layer to mm-scale. These have widely variable microstructure with transition temperatures ranging from 1.2 K to the current record, 203 K. In all cases the critical current is governed by a fundamental surface current density limit given by the relevant critical field divided by the penetration depth.
超导体中的普遍标度行为极大地阐明了这些材料中的涨落和相变现象。然而，对于最实用的特性——临界电流，并没有考虑到普遍行为，因为流行的模型涉及磁通涡旋的成核和迁移。这种迁移严重依赖于钉扎，并且详细的微观结构自然因材料而异，即使在同一材料中也是如此。通过微观结构工程，在依赖于磁场的临界电流方面不断取得进步，从而说明了其非普遍性行为。但是在这里，我们证明了任何对称性、几何形状或能带多重性的任何超导体的自场临界电流的普遍尺寸标度。我们分析的关键是样品尺寸范围很广，从单原子层到毫米级。这些样品具有广泛变化的微观结构，转变温度范围从 1.2 K 到当前的记录 203 K。在所有情况下，临界电流都受到由相关临界场除以穿透深度给出的基本表面电流密度限制的控制。
