Non-empirical Study of Superconductivity in Alkali-doped Fullerides Based on Density Functional Theory for Superconductors

TL;DR

This study uses density functional theory for superconductors to predict transition temperatures in alkali-doped fullerides, revealing discrepancies with experiments and suggesting the need for more advanced theoretical models.

Contribution

It applies SCDFT with LDA to alkali-doped fullerides to calculate Tc from first principles, highlighting limitations of current theoretical frameworks.

Findings

Calculated Tc values are about 60% lower than experimental data.

Results indicate the need to go beyond Migdal-Eliashberg theory.

First-principles approach provides insights into superconductivity mechanisms.

Abstract

We apply the density functional theory for superconductors (SCDFT) based on the local-density approximation (LDA) to alkali-doped fullerides A3C60 with the face-centered cubic structure. We evaluate the superconducting transition temperature (Tc) from first principles considering energy dependence of electron-phonon coupling, the mass renormalization, and the retardation effect. The calculated Tc=7.5, 9.0 and 15.7 K for A=K, Rb, Cs are approximately 60 % smaller than the experimentally observed values. Our results strongly suggest necessity to go beyond the framework of the Migdal-Eliashberg theory based on the LDA.