Ground state of Hubbard model on 2 × 2 × 2 lattice

Bo-Xiao Zheng, Garnet Kin‐Lic Chan

Takashi Yanagisawa, Yukihiro Shimoi

We investigate the ground state of the Kondo-Hubbard model employing the recently introduced idea of spin-reflection positivity. It is shown exactly that the Kondo-Hubbard model for $J<0$ and $U>|J|/4$ at half filling has a unique ground state which can be ferromagnetic or singlet according to the lattice structure. In particular, for the Kondo lattice with $U>|J|/4$, the ground state is a singlet. We also show a theorem for the Kondo-Hubbard model with the anisotropic antiferromagnetic coupling ${J}_{\ensuremath{\perp}}>0$ and ${J}_{z}\ensuremath{\le}0$ for $U>|{J}_{z}|/4$.

D. F. Wang

In this work, we introduce a long-range version of the extended Hubbard model. The system is defined on a nonuniform lattice. We show that the system is integrable. The ground state, the ground-state energy, and the energy spectrum are also found for the system. Another long-range version of the extended Hubbard model is also introduced on a uniform lattice, and this system is proven to be integrable.

Yoshihiro Asai

Assa Auerbach

Andreas Mielke

The author investigates the U= infinity Hubbard model on a large class of lattices which are line graphs. The most interesting lattices in this class are line graphs of regular bipartite lattices with N s sites and coordination number k>or=4. The ground state energy and some ground states are given. If the number of electrons N satisfies N s >or=N>or=2N s /k-2, the ground state energy is -4 mod t mod (N s -N). The ground states have no magnetic ordering, they are projections of the ground states at U=0 onto the subspace of states without doubly occupied sites.