Scaling theory vs exact numerical results for spinless resonant level model

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 Uf c and hybridization V. Exact dynamics and thermodynamics of the IRLM are derived numerically for a wide range of Uf c with a given value of V. As Uf c 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 Uf c up to infinite order. As Uf c becomes positive and large, however, exact numerical results deviate from lower order scaling results. In particular, the renormalized hybridization increases monotonically with increasing Uf c in contrast with the scaling theory that suggests another quantum critical point.