Phase controls of molecular compounds by lights

2010 Fiscal Year Self-evaluation Report

• Project Area: New Frontier in Materials Science Opened by Molecular Degrees of Freedom
• Project/Area Number: 20110005
• Research Category: Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)
• Allocation Type: Single-year Grants
• Review Section: Science and Engineering
• Research Institution: The University of Tokyo
• Principal Investigator: OKAMOTO Hiroshi The University of Tokyo, 大学院・新領域創成科学研究科, 教授 (40201991)
• Project Period (FY): 2008 – 2012
• Keywords: 分子性導体 / 光誘起相転移 / 超高速分光 / テラヘルツ分光 / レーザー光電子分光

Research Abstract

分子性(半)導体の特徴的な電子相(金属、電荷秩序、電荷密度波(CDW)、スピン密度波(SDW)、モット絶縁体、等)の出現には、電子間相互作用と同時に多様な分子自由度が本質的な役割を演じている。実際に温度や外場の変化により相転移が生じるとき、その転移点近傍において電子系と分子自由度との相互作用が複雑に絡み合った集団応答が顕著に現れる。これらの集団応答や相転移を能動的に誘起する有効な方法の一つが光励起である。超短パルスレーザー光を照射すると、分子内電子励起や分子間電子移動が瞬時に引き起こされる。この電子励起をきっかけとして、電子系と分子自由度の集団応答、更には相転移を引き起こすことが可能ではないかと考えられる。光による相転移の機構を解明するには、短寿命の光誘起電子相の挙動を広範なエネルギー領域で実時間観測することが必要であり、そのための新しい分光測定手法が求められる。本研究では、各種分子性(半)導体に、高時間分解能ポンププローブ分光、テラヘルツ(THz)時間領域分光、レーザー光電子分光を適用し、電子系と分子自由度の相互作用に基づく集団光応答と光誘起相転移のダイナミクスの精密検出を行い、その機構を解明する。結果を物質開発にフィードバックし物質を最適化することにより、光による超高速かつ高効率の相制御実現を目指す。

Research Products

• [Journal Article] Direct Detection of the Ultrafast Response of Charges and Molecules in the Photoinduced Neutral-to-Ionic Transition of the Organic Tetrathiafulvalene-p-Chloranil Solid (2010)
  • Author(s): H.Uemura, H.Okamoto
  • Journal Title: Phys.Rev.Lett. 105 Pages: 258302-1-258302-4
  • Peer Reviewed
• [Journal Article] Early-Stage dynamics of Light-Matter Interaction Leading to the Insulator to metal Transition in a Charge Ordered Organic Crystal (2010)
  • Author(s): Y.Kawakami, T.Fukatsu, Y.Sakurai, H.Unno, H.Itoh, S.Iwai, T.Sasaki, K.Yamamoto, K.Yakushi, K.Yonemitsu
  • Journal Title: Phys.Rev.Lett. 105 Pages: 246402-1-246402-4
  • Peer Reviewed
• [Journal Article] Observation of ultrafast photoinduced closing and recovery of the spin-density-wave gap in (TMTSF)2PF6 (2009)
  • Author(s): S.Watanabe, R.Kondo, S.Kagoshima, R.Shimano
  • Journal Title: Phys.Rev.B 80(Editor's suggestion) Pages: 220408(R)-1-220408(R)-4
  • Peer Reviewed
• [Journal Article] Optical Modulation of Effective On-Site Coulomb Energy for the Mott Transition in an Organic Dimer Insulator (2009)
  • Author(s): Y.Kawakami, S.Iwai, T.Fukatsu, M.Miura, N.Yoneyama, T.Sasaki, N.Kobayashi
  • Journal Title: Phys.Rev.Lett. 103 Pages: 066403-1-066403-4
  • Peer Reviewed
• [Journal Article] Ferroelectric nature and real-space observations of domain motions in the organic charge-transfer compound tetrathiafulvalene-p-chloranil (2009)
  • Author(s): H.Kishida, H.Takamatsu, K.Fujinuma, H.Okamoto
  • Journal Title: Phys.Rev.B 80 Pages: 205201-1-205201-7
  • Peer Reviewed
• [Presentation] Intense THz light and matter interaction in low dimensional electron systems (2011)
  • Author(s): R.Shimano
  • Organizer: The 3rd International Symposium on Interdisciplinary Materials Science 2011
  • Place of Presentation: Tsukuba, Japan(invited)
  • Year and Date: 20110309-20110310
• [Presentation] New Aspects of Photoinduced Neutral to Ionic Phase Transitions in Organic Molecular Compounds (2010)
  • Author(s): H.Okamoto
  • Organizer: International Conference on Science and Technology of Synthetic Metals 2010
  • Place of Presentation: Kyoto, Japan(invited)
  • Year and Date: 20100704-20100709
• [Presentation] Ultrafast IR and THz Spectroscopy of Photoinduced Insulator to Metal Transition in Highly Correlated Organic System (2010)
  • Author(s): S.Iwai
  • Organizer: International Conference on Dynamic Processes of Photo-Excited State in Solids 2010 (DPC'10)
  • Place of Presentation: Argonne National Laboratory, USA(Invited)
  • Year and Date: 2010-06-25
• [Presentation] Ultrafast Dynamics of Photoinduced Neutral to Ionic Transitions in Organic Molecular Compounds (2009)
  • Author(s): H.Okamoto, H.Uemura
  • Organizer: RIKEN Workshop on "Emergent Phenomena of Correlated Materials", RIKEN
  • Place of Presentation: Wako, Japan(Invited)
  • Year and Date: 20091202-20091204
• [Book] Molecular Electronic and Related Materials ; Control and Probe with Light(Ultrafast photo-induced insulator to metal transition in layered BEDT-TTF based salts) (2010)
  • Author(s): S.Iwai, H.Nakaya, Y.Kawakami
  • Total Pages: 37-58
  • Publisher: Ed.T.Naito, Transworld Research Network, Kerala, India
• [Book] Molecular Electronic and Related Materials ; Control and Probe with Light(Ultrafast photoinduced phase transitions in one-dimensional organic correlated electron systems) (2010)
  • Author(s): H.Okamoto
  • Total Pages: 59-97
  • Publisher: Ed.T.Naito, Transworld Research Network, Kerala, India
• [Book] 有機半導体における光誘起相転移の超高速ダイナミクスとコヒーレント振動(強光子場科学の最前線2) (2009)
  • Author(s): 岡本博
  • Total Pages: 123-138
  • Publisher: 強光子場科学研究懇談会
• [Remarks] ホームページ
  • URL: http://pete.k.u-tokyo.ac.jp/