Antiferromagnetic Interactions and the Superconducting Gap Function

TL;DR

This paper demonstrates that three-dimensional antiferromagnetic spin fluctuations can produce a superconducting state with s-wave symmetry but with line nodes, challenging the conventional association with d-wave pairing.

Contribution

It introduces a generalized model showing that antiferromagnetic fluctuations can lead to s-wave states with line nodes, expanding the understanding of pairing symmetries.

Findings

The s-wave state with line nodes can be more stable than d-wave in certain conditions.

The model uses realistic band structures and both BCS and Eliashberg theories.

Spin-fluctuation models should consider both d-wave and s-wave possibilities.

Abstract

Spin-fluctuation-mediated superconductivity is conventionally associated with d_{x^2-y^2} pairing. We show that a generalized model of antiferromagnetic spin fluctuations in three dimensions may also yield a state with formal ``s-wave'' (A_{1g}) symmetry but with line nodes at k_z \approx \pm \pi / 2c. We study this new state within both BCS and Eliashberg theories using a realistic band structure and find that it is more stable than the d_{x^2-y^2} (B_{1g}) state over a wide range of parameters. Thus, models of spin-fluctuation-mediated superconductivity must consider both possibilities on an equal footing.