Correlation-induced dimensional crossovers of charge-transfer excitations in quasi-one-dimensional organic conductors

Applying the finite-temperature density-matrix renormalization-group method to the spinless fermion model on a two-leg ladder, we have calculated the dynamical structure factors for the local charge transfer processes along and across the chains. The intra-chain excitation spectra are sensitive to the inter-chain transfer integral and the chemical potential, while the inter-chain excitation spectra are sensitive to the intra-chain electron correlation. These dynamical properties are due to the collective motions of fermions along the chains and the energy-dependent confinement of fermions in the chains. At low but finite energies, the effects of the increasing inter-chain transfer integral on the local charge-transfer spectra are similar to those of the chemical potential deviating from zero.