Effects of electron interactions on the oscillator strengths in one-dimensional systems: a density-matrix renormalization group approach

Effects of electron interactions on the oscillator strengths f in one-dimensional extended Hubbard systems are studied by the Lanczos iteration scheme and density-matrix renormalization group algorithm. Detailed calculations reveal that (1) for a small U, such as U=2–3, a roughly linear increase of f with chain length N is observed and virtually unaffected by the ratio U/V; (2) for a large U, for instance, U=5–6, f strongly depends on the ratio and may have a nonlinear dependence on N. U determines the maximal f; (3) for U=5−6 and U/V=1.5, f first increases and then saturates around N=10–16, consistent with the experimental observation.