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arXiv 1008.4833cond-mat.supr-con
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各向异性能谱先进超导体的上临界场Hc2

The Upper Critical Field Hc2 in Advanced Superconductors with Anisotropic Energy Spectrum

M. E Palistrant

摘要:

本文简要回顾了确定双带各向同性和各向异性超导体上临界场的微观理论的工作。该研究是基于一组Ginzburg-Landau方程的序参量在一个磁场,研究在一个超导系统的经典方法在一个磁场。讨论了费米面上重叠的两个不同拓扑费米面腔的不等价能带。研究了外磁场方向H \to //(ab)平面和H \to //晶体学c轴的情况。本文导出了纯超导体和掺杂电子和空穴的超导体的Hc_2(ab)和Hc_2(c)的计算公式。得到了这些方程在超导转变温度(Tc-T <<Tc)附近和零温度(T<<Tc)附近的解析解,研究了上临界场Hc 2(ab)和Hc 2(c)以及各向异性系数\gammaH与温度和杂质的关系。由此产生的理论应用于确定金属间化合物MgB 2的上述磁特性的依赖性。理论与实验数据在性质上是一致的。

英文摘要:

A brief review of works on the microscopic theory of determining the upper critical field in two-band isotropic and anisotropic superconductors is given. The research is based on a set of the Ginzburg-Landau equations for the order parameters in a magnetic field that are studied in terms of the classical approach to a superconducting system in a magnetic field. Two inequivalent energy bands with different topology of Fermi surface cavities overlapping on the Fermi surface are discussed. The cases of the direction of the external magnetic field H\to// the (ab) plane and H\to // the crystallographic c axis are studied. The equations for determining Hc2(ab) and Hc2(c) for a pure superconductor and a superconductor doped with electrons and holes are derived. The analytical solutions to these equations in the vicinity of the superconducting transition temperature (Tc - T<<Tc) and in the vicinity of zero (T<<Tc) are found. The temperature and impurity dependences of the upper critical fields Hc2(ab) and Hc2(c), as well as the anisotropy coefficient \gammaH, are studied. The resulting theory is applied to determine the dependences of the above magnetic characteristics of intermetallic compound MgB2. The theory agrees qualitatively with experimental data.

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