Elementary electronic excitations in one-dimensional continuum and lattice systems

We systematically investigate the mode dispersion and spectral weight of the elementary excitation spectra in one-dimensional continuum and lattice electron systems by using the RPA, the Luttinger liquid model, and the Hubbard model. Both charge and spin excitations are studied in detail and compared among the theoretical models. For the lattice Hubbard model we use both Bethe-ansatz equations and Lanczos-Gagliano method to calculate dispersion and spectral weight separately. We discuss the theoretically calculated elementary excitation spectra in terms of the experimental inelastic light ~Raman! scattering spectroscopy of one-dimensional ~1D! semiconductor quantum wire systems. Our results show that in the polarized ~i.e., non-spin-flip! Ramanscattering spectroscopy, only the 1D charge density excitations should show up with observable spectral weight with the single-particle excitations ~in random-phase approximation! or singlet spin excitations ~in the Luttinger model and the Hubbard model! having negligible spectral weight. The depolarized ~spin-flip! Ramanscattering spectra manifest the spin density or the triplet spin excitations. We also provide a qualitative comparison between the continuum and the lattice 1D elementary excitation spectra.