A Hartree-Fock approach to La2CuO4 properties: hints for matching the   Mott and Slater pictures
  This is extended version of a previously submitted paper, in which special solutions of the Hartree-Fock (HF) problem for Coulomb interacting electrons, being described by a simple model of the Cu-O planes in La2CuO4, are presented. One of the mean field states obtained, is able to predict some of the basic properties of this material, such as its insulator character and the antiferromagnetic order. The natural appearance of pseudogaps in some states of this compound is also indicated by another of the HF states obtained. These surprising results follow after eliminating spin and crystal symmetry restrictions which are usually imposed on the single particle HF orbitals, by means of employing a rotational invariant formulation of the HF scheme which was originally introduced by Dirac. Therefore, it is exemplified how, up to now being considered strong correlation effects, can be described by improving the HF solution of the physical systems. In other words, defining the correlation effects as such ones shown by the physical system and which are not predicted by the best HF (lowest energy) solution, allows to explain currently assumed as strong correlation properties, as simple mean field ones. The discussion also helps to clarify the role of the antiferromagnetism and pseudogaps in the physics of the HTSC materials and indicates a promising way to start conciliating the Mott and Slater pictures for the description of the transition metal oxides and other strongly correlated electron systems. 
Alejandro Cabo-Bizet and Alejandro Cabo-Montes de Oca