S- and D-Wave Pairing in Short Coherence Length Superconductors

TL;DR

This paper develops a unified theoretical framework using Landau-Ginzburg-Wilson effective action to analyze pairing symmetries in the attractive Hubbard model, revealing complex phase behavior including s, d, s+id, and p-wave states.

Contribution

It introduces a comprehensive Landau-Ginzburg-Wilson approach to study pairing symmetries in the Hubbard model, bridging BCS and Bose-Einstein limits.

Findings

Identification of s- and d-wave solutions and their degeneracy in the large V limit.

Discovery of an intermediate s+id phase and an unstable p-wave phase.

Unified description of pairing behavior across different interaction regimes.

Abstract

We derive an appropriate Landau-Ginzburg-Wilson effective action to describe the nearest neighbour attractive Hubbard model. This allows us to discuss both the small V (BCS) limit and the large V (Bose-Einstein) limit within the same framework. The model is particularly interesting as it exhibits both extended s-wave and d-wave solutions as well as an intermediate s+id phase and an unstable p-wave phase. We note that in the large V limit, as pairs become localised on bonds, the s- and d-wave solutions become degenerate.