Functional Integral Approach for an Extended Hubbard Model: N‐Centre Coupling

Abstract

Abstract Generalized susceptibilities are investigated by the functional integral formalism for an extended Hubbard model. This model includes the parts of intra‐atomic and inter‐atomic Coulomb interaction which can be written in terms of occupation number operators. Phase transitions from the paramagnetic phase to long‐range ordered phases which can be ferromagnetic, antiferromagnetic, or charge ordered, are obtained. In the paramagnetic phase, the behaviour of the local‐moment magnitude is studied, and no sharp phase transition associated with the disappearance of the magnetic moments is found.