Continuum vs. discrete flux behaviour in large mesoscopic Bi2Sr2CaCu2O8+δ disks
Continuum vs. discrete flux behaviour in large mesoscopic Bi2Sr2CaCu2O8+δ disks
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DOI：
10.1209/0295-5075/85/17008
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发表时间：
2008-11
期刊：
影响因子：
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通讯作者：
M. Connolly;M. Milošević;S. Bending;J. Clem;T. Tamegai
中科院分区：
文献类型：
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作者：
M. Connolly;M. Milošević;S. Bending;J. Clem;T. Tamegai
扫描霍尔探针和局部霍尔磁强计测量已被用于研究大介观超导盘的磁通分布，其尺寸位于体涡旋和介观涡旋之间的交叉点附近。通过直接绘制磁感应曲线得到的结果可以很好地拟合到假设磁通量在样品中连续分布的解析模型中。然而，在低磁场下，我们确实观察到潜在的离散涡旋结构的清晰特征，并可以解决涡旋团在增加磁场中的介观压缩特征。即使在更高的场中，单涡旋分辨率丢失，我们仍然能够跟踪涡旋模式的构型变化，因为相互竞争的涡旋顺序在“局部”磁化曲线上施加了明确的特征，作为应用场的函数。我们的观察结果与分子动力学数值模拟非常一致，这使我们对系统中离散和连续行为之间交叉的长度尺度有了自然的定义。
Scanning Hall probe and local Hall magnetometry measurements have been used to investigate flux distributions in large mesoscopic superconducting disks with sizes that lie near the crossover between the bulk and mesoscopic vortex regimes. Results obtained by directly mapping the magnetic induction profiles of the disks at different applied fields can be quite successfully fitted to analytic models which assume a continuous distribution of flux in the sample. At low fields, however, we do observe clear signatures of the underlying discrete vortex structure and can resolve the characteristic mesoscopic compression of vortex clusters in increasing magnetic fields. Even at higher fields, where single-vortex resolution is lost, we are still able to track configurational changes in the vortex patterns, since competing vortex orders impose unmistakable signatures on “local” magnetisation curves as a function of the applied field. Our observations are in excellent agreement with molecular-dynamics numerical simulations which lead us to a natural definition of the lengthscale for the crossover between discrete and continuum behaviours in our system.