Ferromagnetism in the Delta chain Hubbard model

Hiromitsu Ueda, Akinori Tanaka, Toshihiro Idogaki

M. Ichimura, Koichi Kusakabe, Shinji Watanabe +1 more

We examined the magnetic property of newly extended \ensuremath{\Delta}-chain Hubbard models which may be relevant to quantum atomic wires formed on solid surfaces. We rigorously show that the extended models exhibit so-called flat-band ferromagnetism, based on the Mielke-Tasaki theorem. Moreover, we numerically find that the ferromagnetic state is stable against some deviations from completely flat band, by using the exact diagonalization method. The present result will be also useful as a guiding principle to design magnetic materials that possibly display the flat-band ferromagnetism.

Wolfgang Nolting, Michael Potthoff, T. Herrmann +1 more

S Liang, H Pang

We have studied the stability of the ferromagnetic state in the infinite- U Hubbard model on quasi-one-dimensional systems of coupled chains using the density matrix renormalization group technique. By studying lattices with up to 4 × 20 sites, we have found the ferromagnetic state to be unstable above the hole density of δ c = 0.22. Beyond δ c , the total spin of the ground state decreased gradually to zero with increasing hole density.

Andreas Mielke, Hal Tasaki

Ben Hur Bernhard