Role of Coulomb interaction in the superconducting properties of CaC6 and H under pressure

TL;DR

This paper investigates how Coulomb interactions influence the superconducting properties of CaC6 and hydrogen under pressure using superconducting density functional theory, emphasizing the roles of electron-phonon and electron-electron interactions.

Contribution

It provides a detailed ab-initio analysis of the combined effects of electron-phonon and Coulomb interactions on superconductivity in CaC6 and H under pressure, including anisotropy and screening effects.

Findings

Coulomb interactions significantly affect the calculated critical temperature (Tc).

Anisotropy of electron-phonon interaction influences superconducting gap structure.

Screening approximations impact the accuracy of Tc predictions.

Abstract

Superconductivity in intercalated graphite CaC6 and H under extreme pressure, in the framework of superconducting density functional theory, is discussed. A detailed analysis on how the electron-phonon and electron-electron interactions combine together to determine the superconducting gap and critical temperature of these systems is presented. In particular, we discuss the effect on the calculated Tc of the anisotropy of the electron-phonon interaction and of the different approximations for screening the Coulomb repulsion. These results contribute to the understanding of multigap and anisotropic superconductivity, which has received a lot of attention since the discovery of MgB2, and show how it is possible to describe the superconducting properties of real materials on a fully ab-initio basis.