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    Université de Fribourg

    Effective Hamiltonian for a half-filled asymmetric ionic Hubbard chain with alternating on-site interaction

    Grusha, I. ; Menteshashvili, Mikheil ; Japaridze, Giorgi I.

    In: International Journal of Modern Physics B, 2016, vol. 30, no. 3, p. 1550260

    We derive an effective spin Hamiltonian for the one-dimensional half-filled asymmetric ionic Hubbard model (IHM) with alternating on-site interaction in the limit of strong repulsion. It is shown that the effective Hamiltonian is that of a spin S = 1/2 anisotropic XXZ Heisenberg chain with alternating next-nearest-neighbor (NNN) and three-spin couplings in the presence of a uniform and a...

    Université de Fribourg

    Variational ground states of the two-dimensional Hubbard model

    Baeriswyl, Dionys ; Eichenberger, David ; Menteshashvili, Mikheil

    In: New Journal of Physics, 2009, vol. 11, p. 075010

    Recent refinements of analytical and numerical methods have improved our understanding of the ground-state phase diagram of the two-dimensional (2D) Hubbard model. Here, we focus on variational approaches, but comparisons with both quantum cluster and Gaussian Monte Carlo methods are also made. Our own ansatz leads to an antiferromagnetic ground state at half filling with a slightly reduced...

    2 results 1