Mean field theory of normal and superconducting heavy fermion systems and oxide superconductors

Abstract

Normal heavy fermion systems may be assumed to have infinitely strong short range electron-electron interaction U within the f-orbital. Formulating the Anderson lattice model in terms of slave bosons and working in mean field approximation the very high masses, high specific heats and high susceptibilities of these materials may be simply understood. Allowing U to be large but finite, a generalisation of the theory allows for the possibility of superconductivity. In an isotropic model estimates of Tcgive values close to experiment. Gap and Hctake BCS values in the weak coupling limit. In a more realistic model, the gap is found to be anisotropic with zeros and other nonuniversal features developing. The model is also applied to high-Tcoxide superconductors. © 1988 IOP Publishing Ltd.