Abstract
Spectral density of local single-particle excitations for the nondegenerate single-impurity Anderson model is calculated for various values of U/πΔ, ≡(T=0), and T, using the finite-T perturbation theory with U/πΔ as the expansion parameter and the Hartree-Fock (HF) approximation for the unperturbed Hamiltonian. For strong Coulomb correlation and at T=0, (ω) is triple peaked in the Kondo region (≃1), double peaked in the intermediate-valence region (0.8≳≳0.5) and single peaked in the region of nearly empty (or full) orbital. As T increases, (ω) goes through various regimes, to end up with two peaks of half-width ∼Δ at the single-particle excitation energies and +U. Thus the only effect of hybridization () at high T and U≫Δ is the lifetime broadening of two sharp resonances obtained for ≡0, all other many-body effects having been washed out. Comparison with finite-T HF results shows that the HF approximation is reasonable (i.e., correlation is weak) for U≲πΔ (1/2π) at low T, but only for U≲Δ at high T.
- Received 8 January 1987
DOI:https://doi.org/10.1103/PhysRevB.36.675
©1987 American Physical Society