2 ELECTRONS IN A ONE-DIMENSIONAL ROCK SALT LATTICE WITH 2 TYPES OF ON-SITE ELECTRON ELECTRON CORRELATION

The problem of two electrons on a one-dimensional (1D) lattice is solved for the case when the lattice unit cell contains two unequivalent sites a and b with two corresponding electron-electron correlation potentials: attractive U(a) and repulsive U(b). It is shown, that the kinematics of the electron-electron scattering in such a system are remarkably different from those of the ordinary 1D Hubbard model because of the presence of the Umklapp processes. Analytical properties of the S-matrix are studied. Ground state properties and excitation spectrum are analysed as functions of U(a) and U(b).