Flux pinning in superconductors
Flux pinning in superconductors
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DOI：
10.1007/978-3-540-44515-9
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发表时间：
2007
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影响因子：
--
通讯作者：
松下 照男
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文献类型：
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作者：
松下 照男
本章介绍了决定第二类超导体中磁通钉扎和电磁现象的各种基本超导性质。内容主要基于Ginzburg-Landau理论，该理论很好地描述了类型2超导体的磁性。超导态和正常态之间能量密度的最大差异是凝聚能密度，它是决定磁通钉扎相互作用强度的关键因素。特别地，证明了量子化磁通线的中心必须处于正常态，这样约瑟夫森电流才不会因超导序参数相位梯度的奇异性而发散。虽然这种结构在量子化的磁通线由洛伦兹力驱动时引入了损耗，但它有助于阻止磁通线移动的磁通钉扎相互作用，从而导致没有能量耗散。文中还给出了超导电子动能密度在确定上临界场中的作用。简要介绍了约瑟夫森效应，即超导电子通过约瑟夫森结中薄绝缘势垒的隧穿效应。讨论了可获得的最大超导电流密度，即去对电流密度。
This Chapter covers various fundamental superconducting properties that determine the flux pinning and electromagnetic phenomena in type-2 superconductors. The content is mostly based on the Ginzburg-Landau theory, which well describes the magnetic properties of type-2 superconductors. The maximum difference in the energy density between the superconducting and normal states is the condensation energy density, which is a key factor that determines the strength of the flux pinning interaction. In particular, it is shown that the center of a quantized flux line must be in the normal state so that the Josephson current does not diverge due to the singularity in the gradient of the phase of the superconducting order parameter. Although this structure introduces a loss when the quantized flux lines are driven by the Lorentz force, it contributes to the flux pinning interaction that prevents the flux lines from moving, which results in no energy dissipation. The role of the kinetic energy density of the superconducting electrons in determining the upper critical field is also shown. The Josephson effect, ie, the tunnelling effect of superconducting electrons through a thin insulating barrier in a Josephson junction, is briefly introduced. The maximum attainable superconducting current density, ie, the depairing current density, is discussed.