掺钴SrFe2As2外延薄膜中的准各向同性上临界场
Psuedo-isotropic upper critical field in cobalt-doped SrFe2As2 epitaxial films
摘要：
本文报道了在Tc ~ 0.5 K范围内，在高达50 T的脉冲磁场中，掺钴SrFe_2As_2外延薄膜的上临界场（H_c ~ 2）随温度和角度的变化关系。对于H平行线c，Hc 2接近于温度的线性函数，而在垂直方向上存在显著的向下曲率，这导致Hc 2比率（γ = Hc 2（垂直）/Hc 2（平行））随温度几乎线性地减小，在Hc 2（0）= 47 T的低温下接近γ = 1。我们测量完整的上临界场相图，包括角度依赖性和模型的数据使用两个波段的理论，使我们能够确定两个波段的各向异性，它们的相对扩散系数，和BCS耦合常数矩阵元素之间的关系。我们发现一个不寻常的两个带的扩散系数之间的关系，有两个各向异性和相反的频带。这种关系是由观察到的局部最大值Hc 2（平行）在低温下。
英文摘要：
The temperature and angular dependence of the upper critical field (Hc2) is reported for cobalt-doped SrFe2As2 epitaxial films between Tc and 0.5 K in pulsed magnetic fields up to 50 T. For H parallel c, Hc2 is close to a linear function of temperature, while in the perpendicular direction there is significant downward curvature that results in an Hc2 ratio (gamma = Hc2(perpendicular)/Hc2(parallel) that decreases nearly linearly with temperature, approaching gamma = 1 at low temperature with Hc2(0) = 47 T. We measure the complete upper-critical field phase diagram including angular dependence and model the data using a two band theory allowing us to determine the anisotropy of both bands, their relative diffusivities, and the relationship between BCS coupling constant matrix elements. We find an unusual relationship between the diffusivities of the two bands, with two anisotropic and opposite bands. This relationship is supported by the observation of a local maximum for Hc2(parallel) at low temperature.
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