Hole dynamics in the two-band model

X. Zotos, Walter Lehr

G. Seibold, E. Sigmund

We investigate the large U limit of the one-and the three-band Hubbard model.It is found that the dynamics of a hole concerning the stabilization of spin fluctuations differs essentially in the two models.We therefore propose an alternative approach of mapping the three-band model onto an effective one-band Hamiltonian which describes the motion of an additional oxygen hole, in contrast to the usual mapping where the hopping of the Cu-O singlet is reduced to the motion ofthe Cu hole alone.

M. Brunner, Fakher F. Assaad, A. Muramatsu

Masashi Akiyama, Yusuke Inokuma, Yoshiaki Ōno

We investigate the strong correlation effect in the spinless electron-hole two-band Hubbard model using the dynamical mean-field theory. At half filling, both the renormalization factor $Z$ and the number of conduction electrons (valence holes) $n_c$ decrease with increasing the interband Coulomb interaction $U$ down to $Z\sim 0.15$ and $n_c\sim 0.1$ for $U_c \sim \mbox{bandwidth}$ at which the first-order Lifshitz transition occurs from a correlated semimetal with a large effective mass $m^*/m=Z^{-1}$ to a band insulator with a finite gap due to the Hartree shift. A slight hole doping $x$ in the band insulator with a large $U>U_c$ yields a remarkable correlated semimetal with $Z\sim 0.1$ at $x\sim 0.01$, where in-gap states emerge above the valence band top and those weights increase with increasing $x$ together with the increase in $Z$ similar to the in-gap states observed in doped Mott insulators.

Indrani Bose, Saurabh Gayen

Hong Q. Ding, William A. Goddard

A CuO chain with one or two holes doped is studied via the two-band Hubbard model in the large-U limit on a finite cluster. The quasiparticle band is ${\mathit{E}}_{\mathit{k}}$\ensuremath{\sim}0.87J cos(2ka) with the bottom at ka=\ensuremath{\pi}/2. The quasiparticles are kinks which have the character of three-spin polarons. The copper spin excitations are incommensurate spin waves. The two doped holes repel each other very slightly, in contrast to the slight attraction in the t-J model. Spin-charge separation also occurs.