Enhancement of Electron-Phonon Coupling in Alkali-Doped Graphene and Thin MgB2 Layers

Abstract

We present first principle investigation of enhancement of the electron-phonon coupling of superconducting alkali-doped graphene (e.g. LiC6-mono) and thin layers of MgB2 using density functional theory (DFT). These systems resemble in many ways, not only in geometry but as well as in electronic structure. Namely, like in alkali-C6, where we have carbon hexagons with alkali adatom in the hollow site, in MgB2 there are boron hexagons with Mg in hollow site. For instance, both theoretical and experimental studies of LiC6-mono proved a possibility of superconductivity in doped graphene. Continuing this investigation, we explored an enhancement of electron-phonon coupling and the raise of critical temperature in LiC6-mono. Inspired by similarity of intercalated graphite with MgB2, we studied the electron-phonon coupling in MgB2 thin films. We used ab-initio calculations of phonon dispersion and electron-phonon-coupling within framework of DFT using Quantum Espresso. Our research included dopant and strain effects on an enhancement of electron-phonon coupling. We demonstrated an increase of electron-phonon coupling and critical temperatures.