Hundness versus Mottness in a three-band Hubbard-Hund model: On the origin of strong correlations in Hund metals

Abstract

Hund metals are multi-orbital systems with moderate Coulomb interaction, $U$, and sizeable Hund's rule coupling, $J<U$, that aligns the spins in different orbitals. They show strong correlation effects, like very low Fermi-liquid coherence scales and intriguing incoherent transport regimes, resulting in bad metallic behavior. But to what extent are these strong correlations governed by Mottness, i.e. the blocking of charge fluctuations close to a Mott insulator transition (MIT) induced by $U$, or by Hundness, a new route towards strong correlations induced by $J$? To answer this question, we study the full phase diagram of a degenerate three-band Hubbard-Hund model on a Bethe lattice at zero temperature using single-site DMFT and the numerical renormalization group as efficient real-frequency multi-band impurity solver. Hund metal behavior occurs in this minimal model for a filling close to $n_d=2$, moderate $U$ and sizeable $J$, the "Hund-metal regime", with strong correlations manifest by a low quasiparticle weight, $Z$. We show that "spin-orbital separation" (SOS) is a generic $J$-induced feature in the whole metallic regime of the phase diagram for $1<n_d<3$ and sizeable $J$: orbital screening occurs at much higher energies than spin screening, below which Fermi-liquid behavior sets in. The low $Z$ can then be explained in terms of the $J$-reduced Fermi-liquid scale. We further show that, in the Hund-metal regime, far from any MIT, Hundness -- the localization of large spins -- is the key player to induce strong correlations. There, physical properties are governed by a broad incoherent energy regime of SOS with intriguing Hund metal physics: large, almost unscreened spins are coupled to screened orbital degrees of freedom.

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• X-Symbols for Non-Abelian Symmetries in Tensor Networks
• Hund electronic correlation in La${}_3$Ni${}_2$O${}_7$ under high pressure
• Dynamical Mean Field Studies of Infinite Layer Nickelates: Physics Results and Methodological Implications
• Orbital differentiation in Hund metals
• Non-Fermi Liquid and Hund Correlation in La${}_4$Ni${}_3$O${}_{10}$ under High Pressure
• Sr${}_2$MoO${}_4$ and Sr${}_2$RuO${}_4$: Disentangling the Roles of Hund's and van Hove Physics
• The Hund-metal path to strong electronic correlations
• Emergence of flat bands and ferromagnetic fluctuations via orbital-selective electron correlations in Mn-based kagome metal
• State- and superstate-sampling in hybridization-expansion continuous-time quantum Monte Carlo
• Differentiating Hund from Mott physics in a three-band Hubbard-Hund model: Temperature dependence of spectral, transport, and thermodynamic properties
• Spin-charge-lattice coupling across the charge density wave transition in a Kagome lattice antiferromagnet
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• Tree tensor-network real-time multiorbital impurity solver: Spin-orbit coupling and correlation functions in Sr${}_2$RuO${}_4$
• Signatures of Hundness in Kagome Metals
• Hund physics landscape of two-orbital system
• Unconventional Hund Metal in a Weak Itinerant Ferromagnet
• Synergy between Hund-driven correlations and boson-mediated Superconductivity
• Global phase diagram of a spin-orbital Kondo impurity model and the suppression of Fermi-liquid scale
• Description of resonant inelastic x-ray scattering in correlated metals
• Uncovering Non-Fermi-Liquid Behavior in Hund Metals: Conformal Field Theory Analysis of an SU(2)$\times$SU(3) Spin-Orbital Kondo Model
• BaOsO${}_3$: A Hund's metal in the presence of strong spin-orbit coupling
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• Heavy-fermions in frustrated Hund's metal with portions of incipient flat-bands
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• Temperature dependence of correlated electronic states in archetypal kagome metal CoSn
• Nature of the Doping-Driven Metal-Insulator Transition in Correlated Electron Systems with strong Hund's Exchange Coupling
• Tuning orbital-selective phase transitions in a two-dimensional Hund's correlated system
• Hubbard-Kanamori model: spectral functions, negative electron compressibility, and susceptibilities
• Electronic correlations and competing orders in multiorbital dimers: a cluster DMFT study
• A unified phase diagram of F-doped LaFeAsO by means of NMR and NQR parameters
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• Novel $J_{\mathrm{eff}}$=3/2 Metallic Phase and Unconventional Superconductivity in GaTa${}_4$Se${}_8$
• Hund bands in spectra of multiorbital systems
• Nematic spectral signatures of the Hund's metal
• Spontaneous layer selective Mott phase in the bilayer Hubbard model
• Interplay of charge and spin fluctuations in a Hund's coupled impurity
• Frozen spin ratio and the detection of Hund correlations
• Spin and charge fluctuations in the two-band Hubbard model
• Entropy and specific heat of the infinite-dimensional three-orbital Hubbard model
• Testing the parquet equations and the U(1) Ward identity for real-frequency correlation functions from the multipoint numerical renormalization group
• Hund flat band in a frustrated spinel oxide
• Clean realization of the Hund physics near the Mott transition: $\mathrm{Ni}{\mathrm{S}}_2$ under pressure
• Dispersion kinks from electronic correlations in an unconventional iron-based superconductor
• Splitting of electronic spectrum in paramagnetic phase of itinerant ferromagnets and altermagnets
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• Observation of Two Cascading Screening Processes in an Iron-based Superconductor
• Exchange interactions in itinerant magnets: the effects of local particle-hole irreducible vertex corrections and SU(2) symmetry of Hund interaction
• Computing local multipoint correlators using the numerical renormalization group
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