A two-band Hubbard-model description of an almost mixed valence system: A new ground state for La

Abstract

Though not quite a 'mixed valence' system, La shows anomalous properties (e.g. low melting and low Debye temperature, high superconducting transition temperature) which are thought to be due to the proximity of the atomic f-level to the Fermi level. To study the influence of the f-band on the ground state, a two-band Hubbard model is used and it is shown that an ansatz for the ground state, constructed by partially suppressing configurations where two d-electrons are on the same ion by allowing one of them to transfer to the f-level, gives a lower ground-state energy than the Hartree-Fock state.