Coulomb suppression of NMR coherence peak in fullerene superconductors

TL;DR

This paper explains the suppression of the NMR coherence peak in fullerene superconductors by modeling Coulomb interactions within Eliashberg theory, showing how electron-electron repulsions dampen the expected NMR signal.

Contribution

It introduces a self-consistent inclusion of frequency-dependent Coulomb interactions and vertex corrections into Eliashberg theory to explain experimental observations.

Findings

Coulomb interactions cause significant damping in the superconducting state.

The model reproduces the experimentally observed suppression of the NMR coherence peak.

Inclusion of vertex corrections enhances the accuracy of the theoretical explanation.

Abstract

The suppressed NMR coherence peak in the fullerene superconductors is explained in terms of the dampings in the superconducting state induced by the Coulomb interaction between conduction electrons. The Coulomb interaction, modelled in terms of the onsite Hubbard repulsion, is incorporated into the Eliashberg theory of superconductivity with its frequency dependence considered self-consistently at all temperatures. The vertex correction is also included via the method of Nambu. The frequency dependent Coulomb interaction induces the substantial dampings in the superconducting state and, consequently, suppresses the anticipated NMR coherence peak of fullerene superconductors as found experimentally.