Ab initio calculations of Hc2 for Nb, NbSe2, and MgB2
Ab initio calculations of Hc2 for Nb, NbSe2, and MgB2
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DOI：
10.1143/jpsj.73.2924
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发表时间：
2004-11-01
影响因子：
1.7
通讯作者：
Kita, T
中科院分区：
文献类型：
--
作者：
Arai, M;Kita, T
我们报告了弱耦合理论下清洁II型超导体Nb、NbSe 2和MgB 2的上临界场H-c2的定量计算。费米面各向异性是充分考虑的能带数据从头计算电子结构计算。Nb和NbSe 2的结果很好地再现了测量的H-C2曲线的温度和方向依赖性，而无需任何可调参数，包括NbSe 2在T-C附近的显著向上曲率。对于MgB_2，当π/σ能隙比接近0.3时，得到了很好的拟合，这与第一性原理强耦合理论[H. J. Choi等人：Nature 418（2002）758]。我们的结果表明费米面各向异性在描述H-c2的重要性。
We report on the quantitative calculations of the upper critical field H-c2 for clean type-II superconductors Nb, NbSe2, and MgB2 within the weak-coupling theory. The Fermi surface anisotropy is fully taken into account by the energy band data from ab initio electronic structure calculations. The results for Nb and NbSe2 excellently reproduce both temperature and directional dependences of measured H-c2 curves without any adjustable parameters, including a marked upward curvature of NbSe2 near T-c. As for MgB2, a good fit is obtained for a pi/sigma gap ratio of similar to0.3, which is close to that from a first-principles strong-coupling theory [H. J. Choi et al: Nature 418 (2002) 758]. Our results indicate the importance of Fermi surface anisotropy in describing H-c2.