Deciding the fate of the false Mott transition in two dimensions by exact quantum Monte Carlo methods

TL;DR

This paper introduces an unbiased quantum Monte Carlo algorithm that conclusively shows the absence of a Mott transition in the half-filled Hubbard model in two dimensions at low temperatures.

Contribution

The authors develop a systematic, error-free QMC method combined with multigrid extrapolation to accurately analyze the Hubbard model in the thermodynamic limit.

Findings

The Hubbard model remains insulating at low temperatures even at weak coupling.

The previously suggested Mott transition at intermediate coupling is not supported by the new results.

The method provides unbiased Green functions and self-energies free from systematic errors.

Abstract

We present an algorithm for the computation of unbiased Green functions and self-energies for quantum lattice models, free from systematic errors and valid in the thermodynamic limit. The method combines direct lattice simulations using the Blankenbecler Scalapino-Sugar quantum Monte Carlo (BSS-QMC) approach with controlled multigrid extrapolation techniques. We show that the half-filled Hubbard model is insulating at low temperatures even in the weak-coupling regime; the previously claimed Mott transition at intermediate coupling does not exist.