Kapcia, KonradRobaszkiewicz, Stanisław2014-01-312014-01-312013-02-13Journal of Physics: Condensed Matter, Vol. 25, No. 6, 065603 (1-8) (2013)0953-8984http://iopscience.iop.org/0953-8984/25/6/065603/http://hdl.handle.net/10593/10005This is an author-created, un-copyedited version of an article accepted for publication in Journal of Physics: Condensed Matter. IOP Publishing Ltd. is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at http://dx.doi.org/10.1088/0953-8984/25/6/065603We have studied the extended Hubbard model with pair hopping in the atomic limit for arbitrary electron density and chemical potential and focus on paramagnetic effects of the external magnetic field. The Hamiltonian considered consists of (i) the effective on-site interaction U and (ii) the intersite charge exchange interactions I, determining the hopping of electron pairs between nearest-neighbour sites. The phase diagrams and thermodynamic properties of this model have been determined within the variational approach (VA), which treats the on-site interaction term exactly and the intersite interactions within the mean-field approximation. Our investigation of the general case shows that the system can exhibit not only the homogeneous phases: superconducting (SS) and nonordered (NO), but also the phase separated states (PS: SS-NO). Depending on the values of interaction parameters, the PS state can occur in higher fields than the SS phase (field-induced PS). Some ground state results beyond the VA are also presented.enextended Hubbard modelatomic limitzero-bandwidth limitshort coherence lengthsuperconductivityphase separationcharge orderingsMott insulatorbarium bismuthatesArtykułhttps://doi.org/10.1088/0953-8984/25/6/065603