Magnetic properties of the Hubbard model on kagome stripes

Abstract

We consider the one-orbital $N$-site repulsive Hubbard model on two kagome-like chains, both of which yield a completely dispersionless (flat) one-electron band. Using exact many-electron ground states in the subspaces with $n\le n_{\max }$ ($n_{\max }\propto N$) electrons, we calculate the square of the total spin in the ground state to discuss magnetic properties of the models. We have found that although for $n<n_{\max }$ the ground states contain fully polarized states, there is no finite region of electron densities $n/\mathcal{N}<1$ ($\mathcal{N}=N/3$ or $\mathcal{N}=N/5$) where ground-state ferromagnetism survives for $\mathcal{N}\to \infty$.

The paper was presented at the 14th Czech and Slovak Conference on Magnetism CSMAG'10 (6.-9. July 2010, Košice, Slovakia)