Quantum criticality in the pseudogap Bose-Fermi Anderson and Kondo models: Interplay between fermion- and boson-induced Kondo destruction

Abstract

We address the phenomenon of critical Kondo destruction in pseudogap Bose-Fermi Anderson and Kondo quantum impurity models. These models describe a localized level coupled both to a fermionic bath having a density of states that vanishes like |ε|^r at the Fermi energy (ε=0) and, via one component of the impurity spin, to a bosonic bath having a sub-Ohmic spectral density proportional to |ω|^s. Each bath is capable by itself of suppressing the Kondo effect at a continuous quantum phase transition. We study the interplay between these two mechanisms for Kondo destruction using continuous-time quantum Monte Carlo for the pseudogap Bose-Fermi Anderson model with 0<r<1/2 and 1/2<s<1, and applying the numerical renormalization-group to the corresponding Kondo model. At particle-hole symmetry, the models exhibit a quantum critical point between a Kondo (fermionic strong-coupling) phase and a localized (Kondo-destroyed) phase. The two solution methods, which are in good agreement in their domain of overlap, provide access to the many-body spectrum, as well as to correlation functions including, in particular, the single-particle Green's function and the static and dynamical local spin susceptibilities. The quantum-critical regime exhibits the hyperscaling of critical exponents and ω/T scaling in the dynamics that characterize an interacting critical point. The (r,s) plane can be divided into three regions: one each in which the calculated critical properties are dominated by the bosonic bath alone or by the fermionic bath alone, and between these two regions, a third in which the bosonic bath governs the critical spin response but both baths influence the renormalization-group flow near the quantum critical point.

16 pages, 16 figures. Replaced with published version, added discussion of particle hole asymmetry

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• Quantum critical local spin dynamics near the Mott metal-insulator transition in infinite dimensions
• Scaling theory of intrinsic Kondo and Hund's rule interactions in magic-angle twisted bilayer graphene
• Critical charge fluctuations in a pseudogap Anderson model
• Entanglement Entropy Near Kondo-Destruction Quantum Critical Points
• Bose-Fermi Anderson Model with SU(2) Symmetry: Continuous-Time Quantum Monte Carlo Study
• Cluster Extended Dynamical Mean Field Approach and Unconventional Superconductivity
• The Aubry-Andre Anderson model: Magnetic impurities coupled to a fractal spectrum
• Vacancy-induced tunable Kondo effect in twisted bilayer graphene
• Quantum criticality in the spin-isotropic pseudogap Bose-Fermi Kondo model: entropy, scaling, and the g-theorem
• Critical local moment fluctuations and enhanced pairing correlations in a cluster Anderson model
• Emergent soft-gap Anderson models at quantum criticality in a lattice Hamiltonian within dynamical mean field theory
• Tunable phase transition in a dissipative two-spin system: A renormalization group study
• Ultraviolet/infrared mixing-driven suppression of Kondo screening in the antiferromagnetic quantum critical metal