Ab Initio Calculations of H_<c2> for Nb, NbSe_2, and MgB_2(Condensed Matter : Electronic Structure, Electrical, Magnetic and Optical Properties)
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概要
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We report on the quantitative calculations of the upper critical field H_<c2> for clean type-II superconductors Nb, NbSe_2, and MgB_2 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 NbSe_2 excellently reproduce both temperature and directional dependences of measured H_<c2> curves without any adjustable parameters, including a marked upward curvature of NbSe_2 near T_c. As for MgB_2, a good fit is obtained for a π/σ gap ratio of 〜0.3, 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>.
- 一般社団法人日本物理学会の論文
- 2004-11-15
著者
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Arai Masao
Computational Materials Science Center (cmsc) National Institute Of Materials Science (nims)
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Kita Takafumi
Division Of Physics Graduate School Of Science Hokkaido University
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