Dynamical nonlinear optical coefficients from the symmetrized density-matrix renormalization-group method

We extend the symmetrized density-matrix renormalization-group method to compute the dynamic nonlinear optical coefficients for long chains. By computing correction vectors in the appropriate symmetry subspace, we obtain the dynamic polarizabilities, (Formula presented), and third-order polarizabilities (Formula presented) of the Hubbard and “U-V” chains in an all transpolyacetylene geometry, with and without dimerization. We rationalize the behavior of (Formula presented) and (Formula presented) on the basis of the low-lying excitation gaps in the system.