THE QUASI-PARTICLE PROPERTIES OF UPT3 AND THE HIGH-T(C) CUPRATES

The dynamic fluctuations due to localized Hubbard type of effective in teractions, U and J, are calculated perturbatively up to second order around the local density approximation (LDA) electronic structure. We have found for UX3 (X = Ir, Pt, or Au), the mass-enhancement factors a re in good agreement with experiment for U = 2eV, and that the trends in the enhancement factors are systematically related to changes in th e underlying LDA electronic structure. As for La2CuO4 we find that the dynamic fluctuations are small despite the large effective interactio n. Further, our approach reproduces the insulating ground state and th e magnetic moment correctly. For the doped case [La2-xBaxCuO4 (x not-e qual 0)] we find that even though the mass enhancement is small, there is a significant broadening of the quasiparticles close to the Fermi energy.