Enhancement of the d_{x^2-y^2} pairing correlation in the two-dimensional Hubbard model: a quantum Monte Carlo study

TL;DR

This study uses quantum Monte Carlo simulations to explore d_{x^2-y^2} superconductivity in the 2D Hubbard model, revealing enhanced pairing correlations near but not at half-filling, with implications for understanding high-temperature superconductivity.

Contribution

It demonstrates the detection of enhanced d_{x^2-y^2} pairing correlations in the 2D Hubbard model using quantum Monte Carlo, emphasizing the importance of finite-size effects and precise level separation.

Findings

Enhanced d_{x^2-y^2} pairing correlations observed near half-filling.

Finite-size effects are crucial for detecting pairing enhancements.

Long-tailed correlations suggest potential superconductivity in the model.

Abstract

Quantum Monte Carlo is used to investigate the possibility of d_{x^2-y^2} superconductivity in the two-dimensional repulsive Hubbard model. A small energy scale relevant to possible pairing requires a care (i.e., sufficiently small level separation between the $k$ points $(\delta k,\pi-\delta k')$ and $(\pi-\delta k'',\delta k''')$ with small $\delta k$'s) to detect enhanced correlations in finite-size studies, as motivated from a previous study on Hubbard ladders. Our calculation indeed detects long-tailed enhancements in the d_{x^2-y^2} pairing correlation when the system is near, but not exactly at, half-filling.