Screening, Coulomb pseudopotential, and superconductivity in alkali-doped Fullerenes

TL;DR

This paper investigates how static screening and Coulomb pseudopotential influence superconductivity in alkali-doped Fullerenes, revealing that screening is crucial and differs from conventional theories due to limited retardation effects.

Contribution

It demonstrates that in alkali-doped Fullerenes, screening plays a key role in superconductivity, challenging the conventional understanding of retardation effects reducing electron-electron repulsion.

Findings

Random phase approximation is accurate up to the Mott transition.

Coulomb pseudopotential is not significantly reduced by retardation effects.

Efficient screening is essential for electron-phonon driven superconductivity.

Abstract

We study the static screening in a Hubbard-like model using quantum Monte Carlo. We find that the random phase approximation is surprisingly accurate almost up to the Mott transition. We argue that in alkali-doped Fullerenes the Coulomb pseudopotential $\mu^\ast$ is not very much reduced by retardation effects. Therefore efficient screening is important in reducing $\mu^{\ast}$ sufficiently to allow for an electron-phonon driven superconductivity. In this way the Fullerides differ from the conventional picture, where retardation effects play a major role in reducing the electron-electron repulsion.