Increasing d-wave superconductivity by on site repulsion

TL;DR

This study demonstrates that on-site electron repulsion can enhance d-wave superconductivity by effectively increasing superexchange interactions and suppressing competing repulsive interactions, revealing a counterintuitive mechanism for superconductivity.

Contribution

The paper introduces a variational Monte Carlo analysis showing how on-site repulsion U enhances d-wave pairing by modulating competing interactions in an extended Hubbard model.

Findings

On-site repulsion U increases superexchange J.

U suppresses the repulsive V interaction.

Enhanced superconductivity observed due to U's effects.

Abstract

We study by Variational Monte Carlo an extended Hubbard model away from half filled band density which contains two competing nearest-neighbor interactions: a superexchange $J$ favoring d-wave superconductivity and a repulsion $V$ opposing against it. We find that the on-site repulsion $U$ effectively enhances the strength of $J$ meanwhile suppressing that of $V$, thus favoring superconductivity. This result shows that attractions which do not involve charge fluctuations are very well equipped against strong electron-electron repulsion so much to get advantage from it.