Fidelity Study of Superconductivity in Extended Hubbard Models

TL;DR

This study investigates how long-range Coulomb interactions affect superconductivity in extended Hubbard models, revealing thresholds where these interactions destabilize superconducting ground states.

Contribution

It provides the first detailed numerical analysis of the impact of extended interactions on superconductivity in Hubbard models using fidelity metrics.

Findings

Nearest and next-nearest neighbor interactions can destabilize superconductivity.

Superconductivity is suppressed above certain interaction thresholds.

Charge fluctuations compete with pairing mechanisms.

Abstract

The Hubbard model with local on-site repulsion is generally thought to possess a superconducting ground-state for appropriate parameters, but the effects of more realistic long-range Coulomb interactions have not been studied extensively. We study the influence of these interactions on superconductivity by including nearest and next-nearest neighbor extended Hubbard interactions in addition to the usual on-site terms. Utilizing numerical exact diagonalization, we analyze the signatures of superconductivity in the ground states through the fidelity metric of quantum information theory. We find that nearest and next-nearest neighbor interactions have thresholds above which they destabilize superconductivity regardless of whether they are attractive or repulsive, seemingly due to competing charge fluctuations.