A local moment approach to the degenerate Anderson impurity model

Abstract

The local moment approach is extended to the orbitally degenerate (SU(2N)) Anderson impurity model (AIM). Single-particle dynamics are obtained over the fullrange of energy scales, focusing on particle–hole symmetry in the strongly-correlated regimewhere the onsite Coulomb interaction leads to many-body Kondo physics with entangledspin and orbital degrees of freedom. The approach captures many-body broadening of theHubbard satellites and recovers the correct exponential vanishing of the Kondo scale for allN, and its universal scaling spectra are found to be in very good agreement withnumerical renormalization group (NRG) results. In particular the high-frequencylogarithmic decays of the scaling spectra, obtained here in closed form for arbitraryN, coincide essentially perfectly with available numerics from the NRG. A particular case ofan anisotropic Coulomb interaction, in which the model represents a system ofN ‘capacitivelycoupled’ SU(2) AIMs, is also discussed. Here the model is generally characterized by two low-energy scales,the crossover between which is seen directly in its dynamics.