Momentum-dependent pseudogaps in the half-filled two-dimensional Hubbard model

TL;DR

This study uses advanced quantum Monte Carlo simulations to analyze the pseudogap phenomena in the two-dimensional Hubbard model, revealing momentum-dependent charge gaps and their relation to magnetic fluctuations, relevant for cold atom experiments.

Contribution

First unbiased spectral functions of the 2D Hubbard model are computed, clarifying the origin and temperature dependence of the pseudogap.

Findings

Pseudogap appears at weak to intermediate coupling due to momentum-selective charge gap opening.

The pseudogap temperature T* matches the DMFT critical temperature for antiferromagnetic fluctuations.

Results suggest pseudogap physics can be observed in cold atom experiments.

Abstract

We compute unbiased spectral functions of the two-dimensional Hubbard model by extrapolating Green functions, obtained from determinantal quantum Monte Carlo simulations, to the thermodynamic and continuous time limits. Our results clearly resolve the pseudogap at weak to intermediate coupling, originating from a momentum selective opening of the charge gap. A characteristic pseudogap temperature T*, determined consistently from the spectra and from the momentum dependence of the imaginary-time Green functions, is found to match the dynamical mean-field critical temperature, below which antiferromagnetic fluctuations become dominant. Our results identify a regime where pseudogap physics is within reach of experiments with cold fermions in optical lattices.