Quantum critical properties of the Bose-Fermi Kondo Model in a large-N limit

Abstract

Studies of non-Fermi liquid properties in heavy fermions have led to the current interest in the Bose-Fermi Kondo model. Here we use a dynamical large-N approach to analyze an SU(N)xSU($\kappa N$) generalization of the model. We establish the existence in this limit of an unstable fixed point when the bosonic bath has a sub-ohmic spectrum ($|ω|^{1-ε} \sgn ω$, with $0<\epsilon <1$). At the quantum critical point, the Kondo scale vanishes and the local spin susceptibility (which is finite on the Kondo side for κ<1) diverges. We also find an ω/T scaling for an extended range (15 decades) of ω/T. This scaling violates (for $\epsilon \ge 1/2$) the expectation of a naive mapping to certain classical models in an extra dimension; it reflects the inherent quantum nature of the critical point.

4 pages; v2: included clarifying discussions on why the omega/T scaling (for epsilon >=1/2) violates the naive mapping to classical models in an extra dimension and the implications of this observation about the nature of the QCP; v3: shortened to conform to the PRL length limit

References in corpus (4)

• Fractionalized Fermi liquids
• Quantum phase transitions in the Bose-Fermi Kondo model
• Critical properties of the Fermi-Bose Kondo and pseudogap Kondo models: Renormalized perturbation theory
• The pseudogap Fermi-Bose Kondo model

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