Global Phase Diagram of a Spin-Orbital Kondo Impurity Model and the Suppression of Fermi-Liquid Scale

Wang, Y.; Walter, E.; Lee, Seung-Sup B.; Stadler, K. M.; Delft, Jan von; Weichselbaum, Andreas; Kotliar, Gabriel

doi:10.1103/physrevlett.124.136406

Cited by 15 publications

(11 citation statements)

References 80 publications

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“…(This argumentation is entirely analogous to that familiar from the two-channel Kondo model [33]; for the present 3soK model, it is further elaborated in Ref. [49]. )…”

Section: Model Perturbative Rg Flowmentioning

confidence: 59%

Uncovering Non-Fermi-Liquid Behavior in Hund Metals: Conformal Field Theory Analysis of an SU(2)×SU(3) Spin-Orbital Kondo Model

et al. 2020

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Hund metals have attracted attention in recent years due to their unconventional superconductivity, which supposedly originates from non-Fermi-liquid (NFL) properties of the normal state. When studying Hund metals using dynamical mean-field theory, one arrives at a self-consistent "Hund impurity problem" involving a multiorbital quantum impurity with nonzero Hund coupling interacting with a metallic bath. If its spin and orbital degrees of freedom are screened at different energy scales, T sp < T orb , the intermediate energy window is governed by a novel NFL fixed point, whose nature had not yet been clarified. We resolve this problem by providing an analytical solution of a paradigmatic example of a Hund impurity problem, involving two spin and three orbital degrees of freedom. To this end, we combine a state-ofthe-art implementation of the numerical renormalization group, capable of exploiting non-Abelian symmetries, with a generalization of Affleck and Ludwig's conformal field theory (CFT) approach for multichannel Kondo models. We characterize the NFL fixed point of Hund metals in detail for a Kondo model with an impurity forming an SUð2Þ × SUð3Þ spin-orbital multiplet, tuned such that the NFL energy window is very wide. The impurity's spin and orbital susceptibilities then exhibit striking power-law behavior, which we explain using CFT arguments. We find excellent agreement between CFT predictions and numerical renormalization group results. Our main physical conclusion is that the regime of spinorbital separation, where orbital degrees of freedom have been screened but spin degrees of freedom have not, features anomalously strong local spin fluctuations: the impurity susceptibility increases as χ imp sp ∼ ω −γ , with γ > 1.

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“…(This argumentation is entirely analogous to that familiar from the two-channel Kondo model [33]; for the present 3soK model, it is further elaborated in Ref. [49]. )…”

Section: Model Perturbative Rg Flowmentioning

confidence: 59%

Uncovering Non-Fermi-Liquid Behavior in Hund Metals: Conformal Field Theory Analysis of an SU(2)×SU(3) Spin-Orbital Kondo Model

et al. 2020

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“…At very low temperatures (not accessible with CT-HYB), the frozen moments will be screened [33] and the entropy of the resulting strongly renormalized Fermi liquid will go to zero as T → 0. This physics has been demonstrated and explored in recent DMFT studies employing the numerical renormalization group (NRG) impurity solvers [49], and in related works on multiorbital impurity models [53,54].…”

Section: A Entropy Surfacesmentioning

confidence: 95%

“…Recent studies have considered the entropy of multiorbital impurity models in the very low-temperature regime and revealed plateaus associated with the appearance of unscreened moments [53,54]. Here, we present a systematic study of the entropy of the three-orbital lattice system, focusing on the intermediate-and high-temperature regime and on the case of ferromagnetic Hund's coupling.…”

Section: Introductionmentioning

confidence: 99%

Entropy and specific heat of the infinite-dimensional three-orbital Hubbard model

Yue

Werner

2020

Phys. Rev. B

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The Hund's coupling in multiorbital Hubbard systems induces spin freezing and associated Hund metal behavior. Using dynamical mean-field theory, we explore the effect of local moment formation, spin, and charge excitations on the entropy and specific heat of the three-orbital model. For fillings 2 n < 3 and low temperature, we demonstrate a substantial enhancement of the entropy in the spin-frozen metal phase to values comparable to the half-filled Mott insulator. We also discuss the appearance of entropy plateaus and peaks in the specific heat associated with the activation of spin and charge fluctuations at high temperature. The temperature scale for charge excitations is almost independent of filling and given by ≈0.2U , with U the intraorbital repulsion. Local spin excitations become relevant for filling n > 1 and their characteristic temperature is proportional to the Hund coupling J, with a filling-dependent prefactor. The analysis of the specific heat in the atomic limit yields accurate predictions for these features in the strong-coupling regime.

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“…As a result, the channel-symmetric 3CK point Γ = 1 separates two distinct phases, namely the 2CK non-Fermi liquid phase for Γ < 1 and the 1CK Fermi liquid phase for Γ > 1. Recently, the global phase diagram of the three-channel spin-orbital Kondo model, which is relevant for Hund metals, has been studied using the NRG method 35 . We adopted the NORG approach to study the critical behavior in the 2CK and 3CK models.…”

Section: Is Given By Hmentioning

confidence: 99%

Order parameter for the multichannel Kondo model at quantum criticality

Zheng

He²,

Lu³

2021

Phys. Rev. B

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A multi-channel Kondo model, where two or more equivalent but independent channels of electrons compete to screen a spin-1/2 impurity, shows overcompensation of the impurity spin, leading to the non-Fermi liquid behavior in various thermodynamic and transport properties. However, when the channel symmetry is broken, an impurity quantum phase transition can occur at zero temperature. Identification of an order parameter describing the impurity quantum phase transition is very difficult since it is beyond the conventional Landau-Ginzburg-Wilson theory. By employing the natural orbitals renormalization group method, we have studied both two-channel and three-channel Kondo models, from the perspective of spin correlation between the impurity and electrons in electronic channels. Here we demonstrate that by introducing spin correlation ratio as an order parameter we can characterize impurity quantum phase transitions driven by channel asymmetry. Especially the universal critical exponents β of spin correlation ratio and ν of correlation length are explicitly determined by finite-size scaling analysis, namely β = 0.10(1), ν = 2.0(1) and β = 0.10(1), ν = 2.5(1) for the two-channel and three-channel Kondo models, respectively.

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Global Phase Diagram of a Spin-Orbital Kondo Impurity Model and the Suppression of Fermi-Liquid Scale

Cited by 15 publications

References 80 publications

Uncovering Non-Fermi-Liquid Behavior in Hund Metals: Conformal Field Theory Analysis of an SU(2)×SU(3) Spin-Orbital Kondo Model

Uncovering Non-Fermi-Liquid Behavior in Hund Metals: Conformal Field Theory Analysis of an SU(2)×SU(3) Spin-Orbital Kondo Model

Entropy and specific heat of the infinite-dimensional three-orbital Hubbard model

Order parameter for the multichannel Kondo model at quantum criticality

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