Electron-phonon interaction and pairing mechanism in superconducting Ca-intercalated bilayer graphene

TL;DR

This study uses advanced ab initio calculations to analyze the electron-phonon interactions in Ca-intercalated bilayer graphene, revealing phonon-mediated superconductivity with a critical temperature around 7-8 K and distinct superconducting gaps.

Contribution

It provides the first detailed ab initio analysis of the pairing mechanism in Ca-intercalated bilayer graphene, highlighting the role of Ca vibrations and predicting multiple superconducting gaps.

Findings

Superconductivity with T_c = 6.8-8.1 K consistent with experiments.

Low-energy Ca_xy vibrations are crucial for pairing.

Presence of two distinct superconducting gaps on different Fermi surface pockets.

Abstract

Using the {\it ab initio} anisotropic Eliashberg theory including Coulomb interactions, we investigate the electron-phonon interaction and the pairing mechanism in the recently-reported superconducting Ca-intercalated bilayer graphene. We find that C$_6$CaC$_6$ can support phonon-mediated superconductivity with a critical temperature $T_{\rm c}=$6.8-8.1~K, in good agreement with experimental data. Our calculations indicate that the low-energy Ca$_{xy}$ vibrations are critical to the pairing, and that it should be possible to resolve two distinct superconducting gaps on the electron and hole Fermi surface pockets.