J. Kaczmarczyk, J. Spałek, T. Schickling, F. Gebhard, J. Buenemann
A systematic diagrammatic expansion for Gutzwiller-wave function (DE-GWF) is used for the description of superconducting state in the Hubbard model. The method allows for an analysis of the superconducting-gap evolution between the weak and the strong-coupling limits. The superconducting gap at the Fermi surface resembles d-wave only near and at the optimal doping and the corrections to this state are determined; they are coming from the longer range nature of the resulting pairing. The superconducting state appears only for U/t > 3 and for the doping \delta < 0.32; the latter agrees very well with experimental results for the cuprates. The spontaneous breakdown of the Fermi-surface coherence (formation of the Fermi pockets) in the antinodal direction is also discussed. General effective Hamiltonian with pairing is defined in a fully self-consistent manner.
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http://arxiv.org/abs/1210.6249
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