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Exact dynamics of charge fluctuations in the multichannel interacting resonant level model

A modified version of the spinless Anderson model is studied by means of the continuous-time quantum Monte Carlo method. This study is motivated by the peculiar heavy-fermion behavior observed in certain Samarium compounds, which is insensitive to magnetic field. The model involves M channels for conduction electrons, all of which interact with local f electron via the Coulomb repulsion Ufc, while only one channel has hybridization with the local state. The effective hybridization is reduced by the Anderson orthogonality effect, and a quantum critical point occurs with increasing M and/or increasing Ufc. The numerical results at finite temperature of the local charge susceptibility are well fitted by a simple scaling theory for all M. However, the single-particle spectrum is described by a double Lorentzian for M>1, in contrast with the single Lorentzian with M=1. A quasi-particle perturbation theory is presented that reproduces the quantum critical point for large M. The quasi-particle theory gives not only the renormalized energy scale, but its extrapolation toward higher energies being consistent with the double Lorentzian spectrum.