Abstract : The four site Hubbard model is considered from the exact diagonalization and variational method points of view. We show that a symmetry projected mean-field theory recovers the exact ground state energy, irrespective of the interaction strength, in contrast to the conventional Gutzwiller wave-function that will be also considered.
A. Leprévost. Exact ground state of strongly correlated electron systems from symmetry-restored wave-functions. Computational Challenges in Nuclear and Many-Body Physics, Sep 2014, Stockholm, Sweden. ⟨in2p3-01073840⟩