Universal lower limit on vortex creep in superconductors
Universal lower limit on vortex creep in superconductors
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DOI：
10.1038/nmat4840
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发表时间：
2017-04-01
期刊：
影响因子：
41.2
通讯作者：
Civale, L.
中科院分区：
文献类型：
--
作者：
Eley, S.;Miura, M.;Civale, L.
超导体是研究涡旋、拓扑激发的极好实验平台，这些现象也出现在超流体、液晶和玻色-爱因斯坦凝聚体中。涡旋运动可能是破坏性的;它可能导致相变（1），振荡器中的毛刺（2）和超导微波电路中的损耗（3），并且它限制了超导体的载流能力（4）。理解涡旋动力学从根本上和技术上都很重要，而热能和由材料无序定义的能量势垒之间的竞争还没有完全理解。具体来说，早期对铁基超导体中热激活涡旋运动（蠕变）的测量揭示了与YBa 2Cu 3 O 7-delta测量相当的快速率（S）（参考文献5-10）。这是令人困惑的，因为S被认为与金兹伯格数（Gi）有关，而大多数铁基超导体的Gi明显低于YBa 2Cu 3 O 7-δ。在这里，我们报告了BaFe_2（As_（0.67）P_（0.33））（2）薄膜中非常缓慢的蠕变，并提出了类似于Gi（1/2）（T/T-c）（T-c是超导转变温度）的普遍最小可实现S的存在，该S在我们的薄膜和少数其他材料中已经实现，并且没有被违反。这一限制为设计具有缓慢蠕变的材料以及材料参数与涡流动力学之间的相互作用提供了新的线索。
Superconductors are excellent testbeds for studying vortices, topological excitations that also appear in superfluids, liquid crystals and Bose-Einstein condensates. Vortex motion can be disruptive; it can cause phase transitions(1), glitches in pulsars(2), and losses in superconducting microwave circuits(3), and it limits the current-carrying capacity of superconductors(4). Understanding vortex dynamics is fundamentally and technologically important, and the competition between thermal energy and energy barriers defined by material disorder is not completely understood. Specifically, early measurements of thermally activated vortex motion (creep) in iron-based superconductors unveiled fast rates (S) comparable to measurements of YBa2Cu3O7-delta (refs 5-10). This was puzzling because S is thought to somehow correlate with the Ginzburg number (Gi), and Gi is significantly lower in most iron-based superconductors than in YBa2Cu3O7-delta. Here, we report very slow creep in BaFe2(As0.67P0.33)(2) films, and propose the existence of a universal minimum realizable S similar to Gi(1/2)(T/T-c) (T-c is the superconducting transition temperature) that has been achieved in our films and few other materials, and is violated by none. This limitation provides new clues about designing materials with slow creep and the interplay between material parameters and vortex dynamics.