Differentiating Hund from Mott physics in a three-band Hubbard-Hund model: Temperature dependence of spectral, transport, and thermodynamic properties

TL;DR

This paper investigates how Hund and Mott physics differently influence spectral, transport, and thermodynamic properties in a three-band Hubbard-Hund model, using advanced computational methods to identify distinguishing features.

Contribution

It provides a detailed analysis of temperature-dependent signatures that differentiate Hund metal behavior from Mott insulators within a minimal theoretical model.

Findings

Hund metals show spin-orbital separation with two-stage Kondo screening.

Mott insulators exhibit well-separated Hubbard bands and negligible SOS.

Distinct temperature-dependent fingerprints help distinguish Hundness from Mottness.

Abstract

We study the interplay between Mott physics, driven by Coulomb repulsion U, and Hund physics, driven by Hund's coupling J, for a minimal model for Hund metals, the orbital-symmetric three-band Hubbard-Hund model (3HHM) for a lattice filling of 1/3. Hund-correlated metals are characterized by spin-orbital separation (SOS), a Hund's-rule-induced two-stage Kondo-type screening process, in which spin screening occurs at much lower energy scales than orbital screening. By contrast, in Mott-correlated metals, lying close to the phase boundary of a metal-insulator transition, the SOS window becomes negligibly small and the Hubbard bands are well separated. Using dynamical mean-field theory and the numerical renormalization group as real-frequency impurity solver, we identify numerous fingerprints distinguishing Hundness from Mottness in the temperature dependence of various physical quantities. These include ARPES-type spectra, the local self-energy, static local orbital and spin susceptibilities, resistivity, thermopower, and lattice and impurity entropies. Our detailed description of the behavior of these quantities within the context of a simple model Hamiltonian will be helpful for distinguishing Hundness from Mottness in experimental and theoretical studies of real materials.