I. Hagymasi, K. Itai, J. Solyom
We investigate the behavior of the periodic Anderson model in the presence of $d$-$f$ Coulomb interaction ($U_{df}$). Three different methods are applied: mean-field theory, variational calculation, and exact diagonalization of finite chains. The variational approach is based on the Gutzwiller trial wave function and we numerically optimize the variational parameters. Two quantum critical points (QCPs) exist for a critical value of $U_{df}$, where the valence susceptibility diverges. We derive the critical exponent for the valence susceptibility and investigate how the position of the QCP depends on the parameters of the Hamiltonian. For larger values of $U_{df}$, the Kondo regime is bounded by two first-order transitions. These first-order transitions merge into a triple point at a certain value of $U_{df}$. For even larger $U_{df}$ valence skipping occurs. The results of the three methods are compared in detail.
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http://arxiv.org/abs/1212.4636
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