Um modelo variacional para elétrons em banda estreita semi-cheia

Abstract

We have derived an effective Hamiltonian H for narrow half-filled energy band electrons; It contains one-particle terms (band) as well as two-particle terms (correlations) which are chosen simultaneously to satisfy the variational principle of Statistical Mechanics for the free energy. The calculations were done for a gran-canonical system of s-electrons in a lattice of fixed Hydrogen-like atoms, in the low-temperature region. The use of the variational principle has allowed us to obtain information on the lowest states, as well as on the excited ones.