| Project/Area Number |
15340094
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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 |
Condensed matter physics I
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| Research Institution | National University Corporation Yokohama National University |
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Principal Investigator |
TAKEDA Jun National University Corporation Yokohama National University, Graduate School of Engineering, Associate Professor, 大学院・工学研究院, 助教授 (60202165)
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| Co-Investigator(Kenkyū-buntansha) |
OHNO Kaoru National University Corporation Yokohama National University, Graduate School of Engineering, Professor, 大学院・工学研究院, 教授 (40185343)
KODAIRA Tetsuya National University Corporation Yokohama National University, National Institute of Advanced Science and Technology, Senior Research Scientist, 界面ナノアーキテクトニクス研究センター, 主任研究員 (40356994)
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| Project Period (FY) |
2003 – 2004
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| Project Status |
Completed (Fiscal Year 2004)
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| Budget Amount *help |
¥15,900,000 (Direct Cost: ¥15,900,000)
Fiscal Year 2004: ¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2003: ¥12,300,000 (Direct Cost: ¥12,300,000)
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| Keywords | Organic Radical / TTTA / Photoinduced Phase Transition / Mott Insulator / Magnetic Phase Transition / Two-Photon Excitation / First Principle Calculation / 2光子吸収 / 常磁性反磁性磁気相転移 / ラマン散乱 / 赤外吸収 |
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| Research Abstract |
Since a large first order magnetic phase transition with a wide thermal hysteresis loop over wide temperature range was found in 1,3,5-trithia-2,4,6-triazapentalenyl(TTTA) crystal, an organic radical crystal is expected to be a new type of strong correlated materials suitable for studying photoinduced phase transition(PIPT) phenomena. In this research, we first experimentally and theoretically investigated the PIPT phenomena as well as electronic and magnetic structures of TTTA.
We found that the photoexcitations of the charge-transfer and intramolecular π-πtransition bands (i.e.one-photon excitations) induce a low-temperature(LT) diamagnetic to high-temperature(HT) paramagnetic phase transition with a clear threshold excitation density. This nonlinear behavior shows that the photoexcitations create the HT phase clusters as precursors, and subsequently, if the total size of the clusters is beyond a critical value, the macroscopic HT order is formed in the LT phase crystal. We also found that two-photon excitation optically induces the diamagnetic to paramagnetic phase transition with large nonlinear response.
We investigated theoretically the crystal structures as well as electronic structures by means of the ab-initio molecular dynamics method based on the local density approximation. We found that the LT phase is a Peierls insulator while the HT phase is a Mott insulator.
We also developed a femtosecond real-time pump-probe imaging spectroscopy applicable to irreversible photoreactions such as the PIPT in solids, which allows real-time mapping of frequency-and time-resolved transient absorbance in a wide spectral and temporal region at once.
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