Dispersion of Low-lying Excitaions in Half-filled and Doped 1D Hubbard Model

Ezer Melzer

Wolfram Brenig, A. P. Kampf

青木 秀夫, 浩一 草部

energy calculated via weak coupling perturbation theory captures reasonably well the binding energy at intermediate coupling.A possible extension of the weak coupling expansion to larger clusters is discussed.Dispersion of Low-lying Excitaions in Half-fi I led and Doped 10 Hubbard Model

Himadri Barman, Vidhyadhiraja Sudhindra

Koichi Kusakabe, Hideo Aoki

Dispersions and wave functions of all the low-lying excitations are studied numerically along with the Bethe-ansatz analysis for the finite-U one-dimensional Hubbard model for U=0\ensuremath{\rightarrow}U=\ensuremath{\infty}. We find the following. (i) In addition to conventional charge or spin excitations such as des Cloizeaux--Pearson modes, there are classes of excitations involving both spin and charge degrees of freedom. These include the heavy-mass modes arising from the Doucot-Wen gauge potentials. (ii) As U is increased, some level crossings take place at a crossover region of U\ensuremath{\sim}10t in which low-lying spin- and charge-excitation bands become separated and the antiferromagnetic spin correlation becomes significant. (iii) For systems doped with more than one hole, the heavy-mass modes split into branches.

横井 浩太, Nobuya Maeshima, Ken-ichi Hino

We investigate the properties of low-lying photoexcited states of a one-dimensional (1D) ionic extended Hubbard model at half-filling. Numerical analysis by using the full and Lanczos diagonalization methods shows that, in the ionic phase, there exist low-lying photoexcited states below the charge transfer gap. As a result of comparison with numerical data for the 1D antiferromagnetic (AF) Heisenberg model, it was found that, for a small alternating potential Δ, these low-lying photoexcited states are spin excitations, which is consistent with a previous analytical study [Katsura et al., Phys. Rev. Lett. 103, 177402 (2009)]. As Δ increases, the spectral intensity of the 1D ionic extended Hubbard model rapidly deviates from that of the 1D AF Heisenberg model and it is clarified that this deviation is due to the neutral-ionic domain wall, an elementary excitation near the neutral-ionic transition point.