Effects of Disorder on Charge Orderings and Superconductivity in the System of Coexisting I.pdf

Effects of Disorder on Charge Orderings and Superconductivity in the System of Coexisting Itinerant Electrons and Local Pairs Stanisław Robaszkiewicz and Grzegorz Pawłowski Institute of Physics, A. Mickiewicz University ul. Umultowska 85, 61-614 Poznań, Poland Abstract We study the phase diagrams and thermodynamic properties of a system of coexisting itin- erant electrons and local pairs (LP), in the presence of diagonal disorder. The model considered takes into account both the charge exchange couplings, responsible for superconducting orderings, and the density-density interactions, which can stabilize charge ordered states in the system. De- pending on the strength of the random on-site potential, the interactions and the particle concentra- tions the model is found to exhibit several various phases, including the homogeneous ones: super- conducting (SC), charge density wave (CDW) and nonordered (NO), as well as the phase separated states (CDW-SC and CDW-NO). Running title: “Effects of diagonal disorder on CDW and superconductivity” Keywords: charge orderings, superconductivity, diagonal disorder, boson-fermion model, local pairs. 1 The model of coexisting itinerant electrons and bound electron pairs i.e. the boson-fermion model, has been recently proposed for a description of the superconducting copper oxides and other nonconventional (exotic) superconductors, the chalcogenide glasses, as well as some bipolaronic systems [1-3]. Up to now the studies of the model have been concentrated on the superconducting (SC) and nonordered (NO)