Divergent Precursors of the Mott-Hubbard Transition at the Two-Particle Level

TL;DR

This paper reveals that analyzing the two-particle vertex functions in dynamical mean-field theory uncovers early signs of the Mott-Hubbard transition within the metallic phase, which are not visible at the single-particle level.

Contribution

It demonstrates that the divergence of the local Bethe-Salpeter equation in the charge channel serves as a non-perturbative precursor to the Mott transition, detectable inside the metallic regime.

Findings

Divergence of the Bethe-Salpeter equation signals Mott physics precursors.

Precursors are visible at low temperatures with incoherent spectral features.

Precursors are traceable up to the atomic limit at high temperatures.

Abstract

Identifying the fingerprints of the Mott-Hubbard metal-insulator transition may be quite elusive in correlated metallic systems if the analysis is limited to the single particle level. However, our dynamical mean-field calculations demonstrate that the situation changes completely if the frequency dependence of the two-particle vertex functions is considered: The first non-perturbative precursors of the Mott physics are unambiguously identified well inside the metallic regime by the divergence of the local Bethe-Salpeter equation in the charge channel. At low temperatures this occurs in the region where incoherent high-energy features emerge in the spectral function, while at high temperatures it is traceable up to the atomic-limit.