Variational theory for a finite-U periodic Anderson model: Application to heavy-electron materials.

Abstract

We exhibit a variational wave function for the orbitally nondegenerate Anderson lattice model, which incorporates the effects of onsite Coulomb interaction to deal with essentially metallic systems. The average occupation in the correlated orbitals, the renormalized hybridization matrix element, and the mass enhancement are calculated as a function of Coulomb interaction U and the hybridization matrix element V. Our results for the U\ensuremath{\rightarrow}\ensuremath{\infty} limit are in agreement with the existing results for the infinite-U problem. We show that the infinite-U approximation is a good approximation for a class of materials with U>${\mathit{U}}_{\mathit{c}}$ and V${\mathit{V}}_{\mathit{c}}$. The calculation of the effective mass ${\mathit{m}}^{\mathrm{*}}$ in the heavy-fermion regime shows that it becomes large mainly because of the small hybridization of f electrons with the conduction band rather than because of large Coulomb correlations. The advantages of our approach are briefly discussed.