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By the cluster perturbation theory ͑CPT͒, the single-particle spectra and the density of state for an infinite Hubbard bipartite lattice are studied. At half-filling, the spectral functions exhibit three up-spin and three down-spin bands, and the ferrimagnetic ground state is obtained. The detail of the spectra in the CPT is quite different from that in the Hatree-Fock approximation ͑HFA͒. The spectra are broadened by the on-site interaction U and thus the band gap in the HFA disappears in the CPT for small U although the gap still exists for large U. The spectral weights with different spins are quite different. Besides the quasiparticle spectral weight, there exists an incoherent part in the spectra. The effect of hole doping is to remove spectral weights from two sides to the inside of the gap. With increasing doping, the polarization of the spectra decreases. With increasing U, the polarization of the spectra in the gap is reduced. Due to topological structure of the system, the distributions of the spectral weights created by removing and adding an electron on the different sites of a unit cell are different.

Articles you may be interested inTemperature dependent reflectivity and anisotropic magnetization reversal in magnetically doped quasi-twodimensional charge density wave alloys A 0.01 Nb Se 2 ( A = Cr , Mn , Fe ) J. Appl. Phys. 103, 07D306 (2008); 10.1063/1.2856509 Density-functional study of intramolecular ferromagnetic interaction through m-phenylene coupling unit (II): Examination of functional dependence Effect of Fe cap layers on the spin density waves in epitaxial Cr(001) filmsConsidering interchain interaction and the intrachain next-nearest-neighbor hopping interaction, within the self-consistent-field Hartree-Fock approximation, we deal with two neighboring organic ferromagnetic chains. We take into account the -electrons, the Hubbard repulsion, and antiferromagnetic correlation between -electrons and side radical electrons. It is shown that there appear to be two kinds of charge density waves successively when the next-nearest-neighbor hopping interaction is greater than a critical value, which decreases with the interchain coupling. The first charge density wave is accompanied by a bond order wave and the second one has no lattice distortion. The spin density wave along the main chain is modulated by the charge density wave. It is also found that the interchain coupling and the next-nearest-neighbor hopping integral destabilizes the ferromagnetic ground states.

Two kinds of alignments of two neighboring π-conjugated organic ferromagnetic chains are studied by considering the itinerary of electrons, electron-phonon coupling, the Hubbard repulsion and the interchain coupling. It is shown that the out-of-phase alignment is a more stable ferromagnetic structure than in-phase alignment. For out-of-phase alignment, there is a structure transition at a critical interchain coupling, at which the dimerizations of two chains have the same size and reverse sign. Interchain coupling results in transfer of spin density between each main chain and the side radicals. PACS Number(s): 75.30.Ds, 71.20.Hk, 75.50.D