We show that the two-dimensional density-matrix renormalization analysis is
useful to detect the symmetry breaking in the fermionic model on a triangular
lattice. Under the cylindrical boundary conditions with chemical potentials on
edge sites, we find that the open edges work as perturbation to select the
strongest correlations {\it only in the presence of a long range order}. We
also demonstrate that the ordinary size scaling analysis on the charge gap as
well as that of the local charge density under this boundary condition could
determine the metal-insulator phase boundary, which scales almost perfectly
with the density of states and the exact solutions in the weak and strong
coupling region, respectively.Comment: 5 pages, 7 figure