Spectral densities of the symmetric Anderson model

The spectral density of the single-impurity Anderson model is calculated by a combination of quantum Monte Carlo method to provide data on the Matsubara Green’s function, the maximum-entropy method of image reconstruction to invert numerically the spectral representation, and perturbation theory to provide informative default models. The Kondo central peak of the spectral density is shown to be a universal function of ω/${\mathit{T}}_{\mathit{K}}$ and T/${\mathit{T}}_{\mathit{K}}$ at low frequencies, where ${\mathit{T}}_{\mathit{K}}$ is the Kondo temperature. The higher-frequency side peaks are nonuniversal. With decreasing T/${\mathit{T}}_{\mathit{K}}$ the Kondo peak grows as the screened local moment disappears.