Influence of finite Hund rules and charge transfer on properties of Haldane systems

Abstract

We consider the Kondo-Hubbard model with ferromagnetic exchange coupling , showing that it is an approximate effective model for late transition metal-O linear systems. We study the dependence of the charge and spin gaps ${\Delta }_C$, ${\Delta }_S$, and several spin-spin correlation functions, including the hidden order parameter $Z(\pi )$, as functions of $J_H/t$ and $U/t$, by numerical diagonalization of finite systems. Except for $Z(\pi )$, all properties converge slowly to the strong-coupling limit. When $J_H/t\sim 2$ and $U/t\sim 7$ (the effective parameters that we obtain for Y_2BaNiO_5), ${\Delta }_S$ is roughly half of the value expected from a strong-coupling expansion.

6 pages in RevTeX, 8 ps figures. Accepted to be published in Phys. Rev. B

References in corpus (4)

• Specific Heat of defects in the Haldane System Y_2BaNiO_5
• Optical properties of an effective one-band Hubbard model for the cuprates
• Bosonization Approach to the One-Dimensional Kondo Lattice Model at Half Filling: Reexamination
• Spin dynamics of hole doped Y2BaNiO5