PHASE-SEPARATION AND SUPERCONDUCTIVITY IN STRONGLY INTERACTING ELECTRON-SYSTEMS

Phase separation (PS) is a generic feature of electron systems in the presence of strong interaction: When the local electron-electron (e-e) repulsion drastically reduces the electron kinetic energy, the additi on of short-range interactions drives the system to a PS instability i n the absence of long-range Coulomb repulsion. When this latter is pre sent, incommensurate charge-density-waves replace the PS region. The p henomenon of PS has been shown to occur irrespective to the nature of the short range interaction and it is present in models with magnetic, nearest-neighbor Coulombic or electron-lattice interactions. Moreover , Cooper instabilities take place close to the PS regions, as a result of the attractive effective interaction, which eventually lead to PS. Superconductivity (SC) also acts to (partially) stabilise the system reducing the regions of the phase-diagram where PS is present.