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|Date and time:||4th February (Thu.) 16:00〜|
|Place:||SPring-8, "HOUKOUKAN" seminar room|
|Title:||Numerical study of quarter-filled extended Hubbard model coupled to Ising chain in 1D|
|講演者:||大塚雄一 氏 （理研、JST-CREST）|
|Speaker:||Dr. Yuichi Otsuka (Riken, JST-CREST)|
π-d systems, in which itinerant π-electrons are coupled to localized d-electrons,
have recently attracted much interest in the field of the molecular conductors.
Among them, the one-dimensional (1D) conductor TPP[Fe(Pc)(CN)2]2
has been intensively studied ,
which is found to show giant negative magnetoresistance (MR) 
owing to the coupling between the π-electrons on Pc and Fe d-spins.
In order to understand the origin of such intriguing properties,
we have performed Monte Carlo simulations on a 1D π-d coupled model,
where the quarter-filled extended Hubbard model for the π-electrons and
the antiferromagnetic (AF) Ising chain for the d-spins interact
via intramolecular ferromagnetic Hund's-rule coupling.
We find that the AF correlation among the d-spins,
combined with the inter-site Coulomb interaction,
considerably enhances the charge-order correlation in the π-electrons
through the π-d coupling and induces ferromagnetic correlations,
which is consistent with the experimental features.
We also discuss effects of magnetic field on this model
and compare our results with the MR effect.
 T. Inabe, H. Tajima, Chem. Rev. 104 (2004) 5503.
 N. Hanasaki et al., Phys. Rev. B 62 (2000) 5839.