# Extended crossover from Fermi liquid to quasi-antiferromagnet in the half-filled 2D Hubbard model

## TL;DR

This paper investigates how increasing interactions in the half-filled 2D Hubbard model lead to a crossover from Fermi liquid to an insulating state driven by antiferromagnetic correlations, revealing a non-Fermi liquid intermediate phase.

## Contribution

It demonstrates an extended crossover driven by AFM correlations using advanced Monte Carlo and cluster approximation methods, without a sharp metal-insulator transition.

## Key findings

- Long-range AFM correlations induce a crossover from Fermi liquid to insulator.
- An intermediate non-Fermi liquid state with a partially gapped Fermi surface is identified.
- No sharp metal-insulator transition occurs in the studied parameter regime.

## Abstract

The ground state of the Hubbard model with nearest-neighbor hopping on the square lattice at half filling is known to be that of an antiferromagnetic (AFM) band insulator for any on-site repulsion. At finite temperature, the absence of long-range order makes the question of how the interaction-driven insulator is realized nontrivial. We address this problem with controlled accuracy in the thermodynamic limit using self-energy diagrammatic determinant Monte Carlo and dynamical cluster approximation methods and show that development of long-range AFM correlations drives an extended crossover from Fermi liquid to insulating behavior in the parameter regime that precludes a metal-to-insulator transition. The intermediate crossover state is best described as a non-Fermi liquid with a partially gapped Fermi surface.