Excitation Spectrum of Magnetic Impurities in Metals

Abstract

In terms of the nonequivalent-orbital model for dilute magnetic alloys, we have calculated the quasiparticle density of states A_dσ(ω) for the localized-type impurity orbital and A_sσ(ω) for the extended-type impurity orbital. At the band limit (bandwidth W » U) A_dσ(ω) is simply a broad maximum. With decreasing W/U, two broad peaks begin to appear. As W/U decreases further, each peak splits into four sub-peaks as a result of the Coulomb and the exchange interactions between the localized- and the extended-type orbitals. Approaching the atomic limit A_dσ(ω) reduces to the correct two-peak structure. No profound structure has been seen in A_sσ(ω). The quasiparticle lifetimes are also computed, and are about one order of magnitude longer than those found in the Anderson model.