Critical points and non-Fermi liquids in the underscreened pseudogap Kondo model

Abstract

Numerical Renormalization Group simulations have shown that the underscreened spin-1 Kondo impurity model with power-law bath density of states (DOS) $ρ(\w) \propto |\w|^r$ possesses various intermediate-coupling fixed points, including a stable non-Fermi liquid phase. In this paper we discuss the corresponding universal low-energy theories, obtain thermodynamic quantities and critical exponents by renormalization group analysis together with suitable $\epsilon$-expansions, and compare our results with numerical data. Whereas the particle-hole symmetric critical point can be controlled at weak coupling using a simple generalization of the spin-1/2 model, we show that the stable non-Fermi liquid fixed point must be accessed near strong coupling via a mapping onto an effective ferromagnetic $S_\mr{eff}=1/2$ model with singular bath DOS with exponent $r_\mr{eff}=-r<0$. In addition, we consider the particle-hole asymmetric critical fixed point, for which we propose a universal field theory involving the crossing between doublet and triplet levels.

10 pages, 8 figures. Minor modifications in updated version

References in corpus (6)

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Cited by in corpus (6)

• Properties of anisotropic magnetic impurities on surfaces
• Universal crossovers and critical dynamics of quantum phase transitions: A renormalization group study of the pseudogap Kondo problem
• Observation of particle hole asymmetry and phonon excitations in non-Fermi liquid systems: A high-resolution photoemission study of ruthenates
• Kondo-Anderson Transitions
• Quantum phase transitions and thermodynamics of the power-law Kondo model
• Two-channel pseudogap Kondo and Anderson models: Quantum phase transitions and non-Fermi liquids