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Effect of Pressure on Superconducting Ca-intercalated Graphite CaC$_6$

J. S. Kim·L. Boeri·R. K. Kremer·F. S. Razavi
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Abstract

The pressure effect on the superconducting transition temperature ($T_c$) of the newly-discovered Ca-intercalated graphite compound CaC$_6$ has been investigated up to $\sim$ 16 kbar. $T_c$ is found to increase under pressure with a large relative ratio $Δ$$T_c$/$T_c$ of $\approx$ +0.4 %/kbar. Using first-principles calculations, we show that the large and positive effect of pressure on $T_c$ can be explained in the scope of electron-phonon theory due to the presence of a soft phonon branch associated to in-plane vibrations of Ca atoms. Implications of the present findings on the current debate about the superconducting mechanism in graphite intercalation compounds are discussed.

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J. S. Kim, L. Boeri, R. K. Kremer, F. S. Razavi. 2007-01-08. Effect of Pressure on Superconducting Ca-intercalated Graphite CaC$_6$. https://doi.org/10.1103/physrevb.74.214513

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