On the scaling spectrum of the Anderson impurity model

We consider the universal scaling behaviour of the Kondo resonance in the strong-coupling limit of the symmetric Anderson impurity model, using a recently developed local moment approach. The resultant scaling spectrum is obtained in closed form, and is dominated by long tails that in contrast to previous work are found to exhibit a slow logarithmic decay rather than a power-law form, crossing over to characteristic Fermi liquid behaviour on the lowest energy scales. The resultant theory, while naturally approximate, is found to give very good agreement for essentially all frequencies with numerical renormalization group calculations of both the single-particle scaling spectrum and the self-energy.