Spin-fluctuation glue disfavors high-critical temperature of superconductivity?

TL;DR

This study investigates the role of spin fluctuations in high-temperature superconductivity, revealing that certain contributions suppress superconductivity and that magnetic interactions are crucial for understanding pairing mechanisms.

Contribution

It demonstrates that small momentum transfer contributions can suppress superconductivity and highlights the importance of instantaneous magnetic interactions in cuprates.

Findings

Small momentum transfer suppresses superconductivity due to phase frustration.

The pairing gap deviates from the cos kx - cos ky form in cuprates.

Instantaneous magnetic interactions are key to high Tc and pairing gap structure.

Abstract

Antiferromagnetic fluctuations are believed to be a promising glue to drive high-temperature superconductivity especially in cuprates. Here, we perform a close inspection of the superconducting mechanism from spin fluctuations in the Eliashberg framework by employing a typical one-band model on a square lattice. While spin fluctuations can eventually drive superconductivity as is well established, we find that the superconducting tendency is suppressed substantially by a seemingly negligible contribution from a small momentum transfer far away from (pi,pi). This suppression comes from phase frustration of the pairing gap and is expected to be a general feature due to the repulsive pairing interaction of spin fluctuations. Furthermore, we find that the momentum dependence of the pairing gap largely deviates from the functional form of cos kx - cos ky, although this form is well established in cuprate superconductors. We argue that an instantaneous magnetic interaction plays the important role to understand high-critical temperature of superconductivity as well as the momentum dependence of the pairing gap.