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

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.

Mimicking Multiorbital Systems with SU(N) Atoms: Hund’s Physics and Beyond

“…In the case of solid-state multiorbital models, the U-term penalizes spatial charge fluctuations (local occupancies different from the average filling), while the J-term favors high-spin configurations and, to a lesser degree, high orbital angular momentum [1][2][3]. This competition results in an extremely rich scenario of intriguing quantum phases, such as orbital-selective Mott phases (where some bands undergo Mott localization, while others remain metallic) [4][5][6][7], orbital-selective superconductors [8] and the so-called "Hund's metal" [2,[9][10][11][12]. These regimes, besides their conceptual interest, have been invoked to understand the properties of different materials, among which iron-based superconductors [13,14] and ruthenates [15].…”

Electronic structure and magnetic excitations of magnetic superconductors

“…In this case, an orbital-dependent gap should appear in the ordered state for the BFCA sample. This points out that the most likely scenario is for the localization being of a Hund's metal, characterized by spin-orbital energy scale separation [135]. In this scenario, the localization would be a consequence of Hund's coupling in the multiorbital system.…”