  Momentum dependent local-ansatz wavefunction approach (MLA) to the correlated
electron systems in solids has been further developed to solve best a
self-consistent equation for variational parameters at non half-filling. With
use of the improved variational scheme we performed the numerical calculations
for the non-half-filled band Hubbard model on the hypercubic lattice in
infinite dimensions. We verified that the self-consistent scheme significantly
improves the correlation energy and the momentum distribution as compared with
the original scheme in the MLA. We also demonstrate that the theory improves
the standard variational methods such as the Local-Ansatz approach (LA) and the
Gutzwiller wavefunction approach (GA); the ground-state energy in the MLA is
lower than those of the LA and the GA in the weak and intermediate Coulomb
interaction regimes. The double occupation number is shown to be suppressed as
compared with the LA. Calculated momentum distribution functions show a
distinct momentum dependence, which is qualitatively different from those of
the LA and the GA.
