Fate of the false Mott-Hubbard transition in two dimensions

TL;DR

This study shows that in two-dimensional Hubbard models, long-range magnetic fluctuations cause insulating behavior at low temperatures regardless of interaction strength, challenging the traditional Mott-Hubbard transition concept.

Contribution

It demonstrates that long-range fluctuations prevent a true Mott-Hubbard transition in two dimensions, emphasizing the role of Slater-like paramagnons in opening spectral gaps.

Findings

Spectral gap opens due to long-range fluctuations at all interaction strengths.

No true Mott-Hubbard transition occurs in two dimensions at low temperatures.

Long-range magnetic fluctuations dominate the insulating behavior.

Abstract

We have studied the impact of non-local electronic correlations at all length scales on the Mott-Hubbard metal-insulator transition in the unfrustrated two-dimensional Hubbard model. Combining dynamical vertex approximation, lattice quantum Monte-Carlo and variational cluster approximation, we demonstrate that scattering at long-range fluctuations, i.e., Slater-like paramagnons, opens a spectral gap at weak-to-intermediate coupling -- irrespectively of the preformation of localized or short-ranged magnetic moments. This is the reason, why the two-dimensional Hubbard model is insulating at low enough temperatures for any (finite) interaction and no Mott-Hubbard transition is observed.