The magnetic field induced phase separation in a model of a superconductor with local electron pairing

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IOP Publishing Ltd., Temple Circus, Temple Way, Bristol BS1 6BE, England

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We 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.


This 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


National Science Center (NCN) as a research project in years 2011-2013, under grant No. DEC-2011/01/N/ST3/00413; European Commission and Ministry of Science and Higher Education (Poland) - partial financial support from European Social Fund – Operational Programme "Human Capital" – POKL.04.01.01-00-133/09-00 – "Proinnowacyjne kształcenie, kompetentna kadra, absolwenci przyszłości"; The Fundation of Adam Mickiewicz University in Poznań


extended Hubbard model, atomic limit, zero-bandwidth limit, short coherence length, superconductivity, phase separation, charge orderings, Mott insulator, barium bismuthates


Journal of Physics: Condensed Matter, Vol. 25, No. 6, 065603 (1-8) (2013)


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Uniwersytet im. Adama Mickiewicza w Poznaniu
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