Ginzburg-Landau theory of the superheating field anisotropy of layered superconductors
Ginzburg-Landau theory of the superheating field anisotropy of layered superconductors
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层状超导体过热场各向异性的Ginzburg-Landau理论
DOI：
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发表时间：
2016
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通讯作者：
J. Sethna
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作者：
D. Liarte;M. Transtrum;J. Sethna
我们研究了材料各向异性对分层超导体过热场的影响。我们提供了一个直观的论点，既是一个过热领域的存在及其对各向异性的依赖，$ nesuremath {kappa} = nesuremath {lambda}/senuremath {xi} $（磁性与超导愈合长度的比率）小的。一方面，我们的估计值与已发布的结果的组合使用$ {MathRM {MGB}}} _ {2} $的两间隙模型表明，在零温度附近的超热场的高各向异性。另一方面，在金茨堡 - 兰道理论中，对于单个间隙，我们看到，只有当晶体各向异性较大并且金兹堡 - 兰道参数$ senerremath {kappa} $时，过热场才显示出明显的各向异性。然后，我们得出的结论是，对于临界温度附近的典型非常规超导体，预计只有小的各向异性。使用Ginzburg Landau理论的广义形式，我们通过将问题映射到各向同性情况下，对各向异性过热领域进行定量计算，并以各向异性和$ seneruremath和$ seneruremath {kappa} $呈现相位图II，或混合行为（在Ginzburg-Landau理论中）以及预期每个渐近解决方案的区域。我们估计各种不同材料的各向异性，并讨论这些结果对于射频腔对颗粒加速器的重要性。
We investigate the effects of material anisotropy on the superheating field of layered superconductors. We provide an intuitive argument both for the existence of a superheating field, and its dependence on anisotropy, for $ensuremath{kappa}=ensuremath{lambda}/ensuremath{xi}$ (the ratio of magnetic to superconducting healing lengths) both large and small. On the one hand, the combination of our estimates with published results using a two-gap model for ${mathrm{MgB}}_{2}$ suggests high anisotropy of the superheating field near zero temperature. On the other hand, within Ginzburg-Landau theory for a single gap, we see that the superheating field shows significant anisotropy only when the crystal anisotropy is large and the Ginzburg-Landau parameter $ensuremath{kappa}$ is small. We then conclude that only small anisotropies in the superheating field are expected for typical unconventional superconductors near the critical temperature. Using a generalized form of Ginzburg Landau theory, we do a quantitative calculation for the anisotropic superheating field by mapping the problem to the isotropic case, and present a phase diagram in terms of anisotropy and $ensuremath{kappa}$, showing type I, type II, or mixed behavior (within Ginzburg-Landau theory), and regions where each asymptotic solution is expected. We estimate anisotropies for a number of different materials, and discuss the importance of these results for radio-frequency cavities for particle accelerators.