Charge and spin excitation spectra in the one-dimensional Hubbard model with next-nearest-neighbor hopping
S. Nishimoto, T. Shirakawa, and Y. Ohta

We calculate spin and charge excitation spectra of the one-dimensional (1D) quarter-filled Hubbard model with nearest-neighbor $t$ and next-nearest-neighbor $t^\prime$ hopping integrals using the dynamical density-matrix renormalization group technique. We consider a case where $t$ ($&gt0$) is much smaller than $t^\prime$ ($&gt0$). First, we examine the accuracy of our method, based on comparison between our result and exact noninteracting spectrum. Next, we investigate spectra with onsite Coulomb interaction. We find that the spin and charge excitation spectra are essentially the same as those of the 1D quarter-filled Hubbard (and $t$$-$$J$) model for the two 1D chains along the hopping integral $t^\prime$. However, the hopping integral $t$ ($&ltt^\prime$) plays a crucial role in the short-range correlations and low-energy excitaions; ferromagnetic correlation between electrons on neighboring sites is enhanced and pairing correlation between the electrons is induced. Consequently, a spin-triplet superconducting state may be derived.

© 2008 The American Physical Society.