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Intercalant-Driven Superconductivity in YbC$_{6}$ and CaC$_{6}$

I. I. Mazin
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Abstract

Recently deiscovered superconductivity in YbC$_6$ and CaC$_6$ at temperatures substantially higher than previously known for intercalated graphites, raised several new questions: (1) Is the mechanism considerably different from the previously known intercalated graphites? (2) If superconductivity is conventional, what are the relevant phonons? (3) Given extreme similarity between YbC$_6$ and CaCa$_6$, why their critical temperatures are so different? We address these questions on the basis of first-principles calculations and conclude that coupling with intercalant phonons is likely to be the main force for superconductivity in YbC$_6$ and CaC$_6$, but not in alkaline-intercalated compounds, and explain the difference in $T_c$ by the ``isotope effect'' due to the difference in Yb and Ca atomic masses.

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I. I. Mazin. 2005-04-06. Intercalant-Driven Superconductivity in YbC$_{6}$ and CaC$_{6}$. https://doi.org/10.1103/physrevlett.95.227001

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