Nonlocal correlations induced by Hund's coupling: a cluster DMFT study

TL;DR

This study uses cluster DMFT to explore how Hund's coupling influences nonlocal correlations in multiorbital systems, revealing an anomalous electronic state driven by intersite ferromagnetic correlations.

Contribution

It demonstrates that Hund's coupling significantly impacts nonlocal correlations and induces an anomalous metallic state beyond local effects.

Findings

Hund's coupling modulates electron distribution in momentum space.

It induces an anomalous metallic state distinct from Fermi liquid and Mott insulator.

Intersite ferromagnetic correlations are key to the anomalous state.

Abstract

We study spatial correlation effects in multiorbital systems, especially in a paramagnetic metallic state subject to Hund's coupling. We apply a cluster extension of the dynamical mean-field theory (DMFT) to the three-orbital Hubbard model away from half filling, where previous single-site DMFT studies revealed that local correlation effects caused by Hund's coupling bring about unusual strongly-correlated metallic behaviors. We find that Hund's coupling significantly affects the nonlocal correlations, too; it strongly modulates the electron distribution in the momentum space so as to make a momentum region almost half-filled and hence strongly correlated. It leads to an anomalous electronic state distinct both from the Fermi liquid and the Mott insulator. We identify the mechanism of the anomalous state with the intersite ferromagnetic correlations induced by Hund's coupling.