Detection of pairing correlation in the two-dimensional Hubbard model

TL;DR

This study uses Quantum Monte Carlo to investigate a correlated pairing mechanism in the 2D Hubbard model, revealing signs of off-diagonal long-range order near half-filling, which suggests potential superconductivity.

Contribution

It introduces a correlated pairing concept inspired by the t-J model and demonstrates its relevance to superconductivity in the 2D Hubbard model.

Findings

D-wave pairing susceptibility diverges as 1/T near half-filling

Ground-state pairing correlations grow with system size

Evidence of off-diagonal long-range order

Abstract

Quantum Monte Carlo method is used to re-examine superconductivity in the single-band Hubbard model in two dimensions. Instead of the conventional pairing, we consider a `correlated pairing', $\langle \tilde{c}_{i\uparrow} \tilde{c}_{i'\downarrow} %\tilde{c}_{j'\downarrow}^\dagger \tilde{c}_{j \uparrow}^\dagger \rangle$ with $\tilde{c}_{i\sigma} \equiv c_{i\sigma}(1-n_{i-\sigma})$, which is inferred from the $t$-$J$ model, the strong-coupling limit of the Hubbard model. The pairing in the $d$-wave channel is found to possess both a divergence like $1/T$ in the pairing susceptibility and a growth of the ground-state pairing correlation with sample size, indicating an off-diagonal long-range order near (but not exactly at) half-filling.