2003 Fiscal Year Final Research Report Summary
Study on the local structural change associated with the photo-induced phase transition in single crystals of quasi-one dimensional charge-transfer complex TTF-CA.
| Project/Area Number |
13440096
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
固体物性Ⅰ(光物性・半導体・誘電体)
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| Research Institution | Wakayama University |
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Principal Investigator |
ITOH Chihiro Wakayama University, Faculty of Systems engineering, Associate Professor, システム工学部, 助教授 (60211744)
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| Co-Investigator(Kenkyū-buntansha) |
SHIRAI Masanobu Kyoto University, Faculty of Science, Research Associate, 大学院・理学研究科, 助手 (30303803)
AKIMOTO Ikuko Wakayama University, Faculty of Systems engineering, Research Associate, システム工学部, 助手 (00314055)
KAN'NO Ken-ichi Wakayama University, Faculty of Systems engineering, Professor, システム工学部, 教授 (80024339)
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| Project Period (FY) |
2001 – 2003
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| Keywords | TTF-CA crystal / spin soliton / electron-spin echo / ESEEM / pulsed ESR / FT-IR measurement / photo-induced phase transition |
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| Research Abstract |
Crystals of quasi one-dimensional charge-transfer complex TTF-CA show structural phase transition between quasi-neutral phase, in which the donors (TTFs) and the acceptors (CAs) are almost neutral, and quasi-ionic phases, in which the partially ionized TTFs and CAs form heterodimers. Since the discovery of the photo-induced phase transition (PIPT) of the ionic phase of the TTF-CA crystal, many efforts have been made for revealing the PIPT's dynamics. However, identification and characterization of the photo-induced phase (PIP) has not been made yet. In the present study, we carried out electron-spin echo detection of electron spin resonance (ESE-ESR) and Fourier-transformation infrared (FT-IR) measurement for characterizing the PIP of TTF-CA crystal. For proving the local structure of the ionic phase and the PIP, we utilized spin solitons formed between two degenerated structures of the ionic phase as a spin probe. The symmetry and the local structural information of the spin soliton a
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t 4 K was obtained by measuring angular dependence of the ESE-ESR spectra at 4 K, and by using electron-spin echo envelope modulation (ESEEM) technique. The results suggest that the spin soliton has the configuration of unpaired ionized molecule. When the crystal was excited continuously by the 523-nm laser beam having the E vector perpendicular to the stacking axis, the ESE-ESR signal arising from the spin solitons was reduced largely. On the other hand, the excitation with E vector parallel to the stacking axis gave small change. By time-resolved ESE-ESR measurements, the ESR signal due to the spin solitons was largely affected in the μs region even by the excitation with the E vector parallel to the stacking axis. The result suggests that the laser excitation leads to temporal change in the configuration of the spin solitons even when the excitation is insufficient for inducing the phase transition. By FT-IR measurements under weak excitation, we have revealed that the charge-transfer absorption of the crystal was largely affected. The result suggests that the donor-acceptor pairs are partially dissociated. Less
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