Variational theory for the orbital-degenerate periodic Anderson model.

Abstract

The ground state of the periodic Anderson model with orbital degeneracy is investigated in a variational method. The on-site Coulomb repulsion is assumed to be infinite. In particular, the effect of the orbital degeneracy upon the various physical properties is investigated. It is shown that the spin correlation of f electrons, ${S}_{\mathrm{ff}}$(q), is q-independent in the limit of large degeneracy ${N}_{f}$. This means that the ground state can be seen as a collection of the independent f-electron states at each site. It is also proved that the spin susceptibility of f electrons is finite in this limit. The momentum distribution functions are calculated, which indicate that the state of the f electron tends to be localized as ${N}_{f}$ becomes larger. At the same time the spin correlation function of f electrons is reduced and q dependence is suppressed by the large orbital degeneracy. The static spin susceptibility \ensuremath{\chi} and the Wilson ratio R are also evaluated. \ensuremath{\chi} and R are suppressed by the orbital degeneracy and the paramagnetic state becomes more stable compared to ferromagnetic ordering.