Ab initio calculations of H$_{c2}$ for Nb, NbSe2, and MgB2

Masao Arai; Takafumi Kita

doi:10.1143/jpsj.73.2924

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Ab initio calculations of H$_{c2}$ for Nb, NbSe2, and MgB2

Masao Arai·Takafumi Kita

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Abstract

We report on quantitative calculations of the upper critical field $H_{c2}$ for clean type-II superconductors Nb, NbSe$_{2}$, and MgB$_{2}$ using Fermi surfaces from {\em 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 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 $\sim 0.3$, which is close to the value from a first-principles strong-coupling theory [H. J. Choi \textit{et al}. Nature, \textbf{418} 758 (2002)]. Our results indicate essential importance of Fermi surface anisotropy for describing $H_{c2}$.

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Masao Arai, Takafumi Kita. 2004-04-27. Ab initio calculations of H$_{c2}$ for Nb, NbSe2, and MgB2. https://doi.org/10.1143/jpsj.73.2924

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