Correlation effects on the Fermi surface of the two-dimensional Hubbard model

TL;DR

This study uses quantum Monte Carlo simulations to explore how electron correlations influence the Fermi surface in the two-dimensional Hubbard model, revealing temperature-dependent structures and doping effects.

Contribution

It provides new insights into the temperature and doping dependence of the Fermi surface and charge susceptibility in the Hubbard model, aligning with mean-field predictions.

Findings

Peak structure at $(\pm rac{\pi}{2},\pm rac{\pi}{2})$ on the Fermi surface at low temperature

Disappearance of anisotropic charge susceptibility at high temperature

Diminishing of anisotropic structure with increased doping

Abstract

Effects of electron correlation on the Fermi surface is investigated for the two-dimensional Hubbard model by the quantum Monte Carlo method. At first, an infinitesimal doping from the half filling is focused on and the momentum dependent charge susceptibility $\kappa(k)=\frac {dn(k)}{d\mu}$ is calculated at a finite temperature. At the temperature $T \sim \frac {t^2} U$, it shows peak structure at $(\pm \pi/2,\pm \pi/2)$ on the Fermi surface (line). It is consistent with the mean-field prediction of the d-wave pairing state or the staggerd flux state. This momentum dependent structure disappears at the high temperature $T \approx U$. After summarizing the results of the half filling case, we also discuss the effects of the doping on the momentum dependent charge susceptibility. The anisotropic structure at half filling fades out with sufficient doping.