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Finite temperature neutral-ionic transition and lattice dimerization in charge-transfer complexes: QMC study |
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| Authors: | Yuichi Otsuka Hitoshi Seo Kazuyoshi Yoshimi Takeo Kato |
| Institution: | 1. Condensed Matter Theory Laboratory, RIKEN, 2-1, Hirosawa, Wako 351-0198, Japan;2. JST, CREST, 2-1, Hirosawa, Wako 351-0198, Japan;3. Research Institute for Computational Sciences (RICS), National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan;4. Department of Physics, University of Tokyo, Hongo Bunkyo-ku, Tokyo 113-8656, Japan;5. Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan |
| Abstract: | We numerically investigate the neutral-ionic (NI) phase transition on the basis of the ionic extended Hubbard model with electron-lattice coupling as well as inter-chain Coulomb interaction. Finite-temperature (T) phase transitions are examined by a quantum Monte Carlo method, within adiabatic approximation for the lattice displacement together with inter-chain mean-field treatment. The NI transition either with or without the electron-lattice coupling is of first-order at low-T and transforms into a cross-over regime with increasing T. We confirm there exist two phases in the ionic region: with and without lattice dimerization, as suggested in recent experiments. The former is ferroelectric, which is rooted in the Coulomb interactions and a spin-Peierls mechanism. |
| Keywords: | Neutral-ionic transition Lattice dimerization Ferroelectricity Extended Hubbard model Quantum Monte Carlo |
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