Scaling Theory vs Exact Numerical Results for Spinless Resonant Level Model

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This paper studies the charge Kondo effect in the (spinless) interacting resonant level model (IRLM) by means of the continuous-time quantum Monte Carlo method. The charge Kondo effect may be relevant to certain Samarium compounds with peculiar heavy-fermion behavior. We use double expansion with respect to Coulomb interaction U_{fc} and hybridization V. Exact dynamics and thermodynamics of the IRLM are derived numerically for a wide range of U_{fc} with a given value of V. As U_{fc} becomes negative, a quantum critical point is found in excellent agreement with a simple scaling formula that deals with V in the lowest-order, and U_{fc} up to infinite order. As U_{fc} becomes positive and large, however, exact numerical results deviate from lower order scaling results. In particular, the renormalized hybridization increases monotonically with increasing U_{fc} in contrast with the scaling theory that suggests another quantum critical point.
2013-12-15