Selfconsistent investigation of multichannel superconductivity in a cuprate model system

TL;DR

This study develops a multichannel Eliashberg theory to investigate how spin fluctuations and electron-phonon interactions jointly influence high-temperature superconductivity in cuprates, revealing electron-phonon interactions as the primary driver of pairing.

Contribution

The paper introduces a self-consistent multichannel Eliashberg framework that combines spin fluctuations and electron-phonon interactions to explain cuprate superconductivity.

Findings

Electron-phonon interaction mainly drives high $T_c$ and pairing.

Both mechanisms support $d_{x^2 - y^2}$ symmetry of the gap.

Spin fluctuations suppress the gap magnitude and $T_c$.

Abstract

The origin of high-temperature superconductivity in cuprates is still an unresolved issue. Among the most likely candidates for mediating the Cooper pair condensate are spin fluctuations and the electron-phonon interaction. While the former have long been proposed to be responsible for various observables in the superconducting state, the latter has recently been shown to produce unconventional gap symmetries when vertex corrections are self-consistently taken into account. Here, we develop multichannel Eliashberg theory to incorporate both pairing mechanisms. Solving self-consistently the full-bandwidth, anisotropic Eliashberg equations for a cuprate model system we find the characteristic $d_{x^2 -y^2}$ symmetry of the superconducting gap and a reasonable order of magnitude for $T_c$ ($50-120$ K). We further find that both mechanisms support an unconventional $d$-wave symmetry of the order parameter, yet the electron-phonon interaction is chiefly responsible for the Cooper pairing and high $T_c$, whereas the spin fluctuations have a suppressing effect on the gap magnitude and critical temperature.