研究者詳細 - 岸田　英夫

論文 - 岸田　英夫

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Dynamical Valence Fluctuation at the Charge-Density-Wave Phase Boundary in Iodide-Bridged Pt Compound [Pt(chxn)₂I]I₂ 査読有り

S. Takaishi, D. Kawakami, M. Yamashita, M. Sasaki, T. Kajiwara, H. Miyasaka, K. Sugiura, Y. Wakabayashi, H. Sawa, H. Matsuzaki, H. Kishida, H. Okamoto, H. Watanabe, H. Tanaka, K. Marumoto, H. Ito, S. Kuroda

Journal of American Chemical Society 128 巻頁： 6420 - 6425 2006年4月

記述言語：英語掲載種別：研究論文（学術雑誌）

We synthesized a novel iodo-bridged linear chain platinum compound, having the quasi-twodimensional
charge-density-wave (CDW) ground state and the smallest band gap. In this compound, we discovered an anomalous valence state in the boundary region at which the CDW phase alternates in the crystal by means of ESR, X-ray diffuse scattering, STM, and electrical resistivity. This anomalous state can be explained by the fast fluctuation between PtIV-I...PtII and PtII...I-PtIV in the double well potential. This is the first observation of the dynamical fluctuation of the CDW phase among the quasi one-dimensional halogen-bridged complexes.

DOI： 10.1021/ja060193b

Gigantic Optical Stark Effect and Ultrafast Relaxation of Excitons in Single-Walled Carbon Nanotubes 査読有り

A. Maeda, S. Matsumoto, H. Kishida, T. Takenobu, Y. Iwasa, H. Shimoda, O. Zhou, M. Shiraishi, H. Okamoto

Journal of the Physical Society of Japan 75 巻 ( 4 ) 頁： 043709-1 - 043709-4 2006年4月

記述言語：英語掲載種別：研究論文（学術雑誌）

We report a splitting and a shift of exciton absorptions in semiconducting single-walled carbon
nanotubes (SWNTs) by resonant and off-resonant excitation using a fs laser pulse, respectively. This is
the first unambiguous observation of the optical Stark effect of excitons in SWNTs, which is responsible
for their high optical-switching performance. By scrutinizing transient absorption spectra from the midto
near-infrared region (0.1– 0.8 eV), the ultrafast recovery of real carrier excitations characteristic of
bundled structures was attributed to the energy- and charge-transfer processes to metallic SWNTs.

DOI： 10.1143/JPSJ.75.043709

Ultrafast Photoinduced Melting of a Spin-Peierls Phase in an Organic Charge-Transfer Compound, K-Tetracyanoquinodimethane 査読有り

H. Okamoto, K. Ikegami, T. Wakabayashi, Y. Ishige, J. Togo, H. Kishida, H. Matsuzaki

Physical Review Letters 96 巻頁： 037405-1 - 037405-4 2006年1月

記述言語：英語掲載種別：研究論文（学術雑誌）

Ultrafast photoinduced phase transition in a spin-Peierls (SP) system of K-tetracyanoquinodimethane
(K-TCNQ) was studied by femtosecond (fs) reflection spectroscopy. Photocarriers destabilize the SP
phase, resulting in a decrease in molecular dimerization within 400 fs. Such a melting of the SP phase
drives three kinds of coherent oscillations. By comparing the oscillations with the Raman bands activated
by the dimerization, we show that the oscillation of 20 cm1 is due to an LO phonon, and it plays an
important role for the stabilization of the SP phase.

DOI： 10.1103/PhysRevLett.96.037405

Valence Fluctuation and Domain-Wall Dynamics in Pressure-Induced Neutral-to-Ionic Phase Transition of Organic Charge-Transfer Crystal 査読有り

H. Matsuzaki1, H. Takamatsu, H. Kishida and H. Okamoto

Journal of the Physical Society of Japan 74 巻 ( 11 ) 頁： 2925 - 2928 2005年11月

記述言語：英語掲載種別：研究論文（学術雑誌）

A pressure-induced neutral-to-ionic (N–I) transition in tetrathiafulvalene-p-chroranil was studied by
infrared vibration spectra. With increasing pressure, two CO stretching bands probing coexisting N and I
states merge due to rapid valence fluctuations. From the spectral analyses with the exchange-narrowing
model, we derive the pressure dependence of the N–I exchange rate related to the N–I domain-wall
motions, which explains the anomalous increase in conductivity under pressure. We also demonstrate a
para- to ferro-electric transition at 1.5 GPa as well as the N–I transition at 0.95 GPa.

DOI： 10.1143/JPSJ.74.2925

Two-step spin conversion in a cyanide-bridged ferrous square 査読有り

M. Nihei, M. Ui, M. Yokota, L. Han, A. Maeda, H. Kishida, H. Okamoto, H. Oshio

Angewandte Chemie International Edition 44 巻 ( 40 ) 頁： 6484 - 6487 2005年10月

Nonlinear and ultrafast optical response in single-walled carbon nanotubes 査読有り

A. Maeda, S. Matsumoto, H. Kishida, T. Takenobu, Y. Iwasa, M. Shiraishi, M. Ata, H. Okamoto

Journal of Physics: Conference Series 21 巻頁： 177 - 182 2005年5月

記述言語：英語掲載種別：研究論文（学術雑誌）

We measured third-order nonlinear susceptibility (􀀂(3)) spectra in semiconducting single-walled carbon nanotubes (SWNTs) by the 􀀂-scan method. |Im􀀂(3)| is remarkably
enhanced under resonant excitation to the lowest interband transition, reaching 4.2 􀀂 10􀀂6 esu.
A comparison of the transient absorption changes evaluated by degenerate and nondegenerate pump-probe measurements suggests that the resonant enhancement of |Im􀀂(3)| is dominated by a coherent process rather than by incoherent one such as saturation of absorption.

DOI： 10.1088/1742-6596/21/1/029

Third-order optical nonlinearity in regio-controlled polythiophene films 査読有り

H. Kishida, K. Hirota, T. Wakabayashi, H. Okamoto, H. Kokubo, T. Yamamoto

Applied Physics Letters 87 巻頁： 121902-1 – 121902-3 2005年9月

Third-order nonlinear optical spectroscopy in charge-transfer-type conjugated polymers 査読有り

H. Kishida, K. Hirota, T. Wakabayashi, H. Okamoto, B. L. Lee, H. Kokubo, T. Yamamoto

Synthetic Metals 153 巻 ( 1-3 ) 頁： 141 - 144 2005年9月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

We have investigated the linear and third-order nonlinear optical properties in a charge-transfer (CT) type conjugated copolymer, PThQx, which is composed of an electron-donating molecule, thiophene (Th), and electron-accepting one, quinoxaline (Qx), by using the linear absorption, two-photon absorption (TPA), and third-harmonic generation (THG) spectroscopies. In comparison with a homopolymer, polythiophene, the absorption coefficient α of PThQx is significantly reduced, while its third-order nonlinear susceptibility (χ(3)) is unchanged. This indicates that the figure of merit for the nonlinear optical materials, defined as χ(3)/α, is enhanced in PThQx. This enhancement comes from the CT character of the excited states in PThQx, in which a hole and an electron are created on different molecules.

DOI： 10.1016/j.synthmet.2005.07.147

Direct observation of excitons and a continuum of one-dimensional Mott insulators: A reflection-type third-harmonic-generation study of Ni-halogen chain compounds 査読有り

M. Ono, H. Kishida, H. Okamoto

Physical Review Letters 95 巻頁： 087401-1 - 087401-4 2005年8月

記述言語：英語掲載種別：研究論文（学術雑誌）

The third-harmonic-generation (THG) spectrum was measured for a NiBr-chain compound, which is a
one-dimensional Mott insulator, in a reflection configuration. A sharp peak and a shoulder structure in the
THG spectrum are attributed to three-photon resonance to an exciton and a continuum, respectively. The
band-edge energy, the exciton binding energy, and the spectral weights for the exciton and the continuum
were determined from comparative studies of linear absorption, THG, and electroreflectance spectra. The
excitonic effect is more pronounced in the NiCl chain than in the NiBr chain.

DOI： 10.1103/PhysRevLett.95.087401

Real-space observation of ferroelectric domains in organic charge-transfer complexes by electromodulation method 査読有り

H. Kishida, K. Fujinuma, H. Takamatsu, H. Okamoto

Transaction of the Materials Research Society of Japan 30 巻 ( 1 ) 頁： 75-78 2005年3月

Vapochromic Behavior Accompanied by Phase Transition between Charge-Polarization and Charge-Density-Wave States in a Quasi-One-Dimensional Iodine-Bridged Dinuclear Platinum Compound 査読有り

H. Matsuzaki, H. Kishida, H. Okamoto, K. Takizawa, S. Matsunaga, S. Takaishi, H. Miyasaka, K. Sugiura, M. Yamashita

Angewandte Chemie International Edition 44 巻 ( 21 ) 頁： 3240 - 3243 2005年5月

Large Optical Nonlinearity of Semiconducting Single-Walled Carbon Nanotubes under Resonant Excitations 査読有り

A. Maeda, S. Matsumoto, H. Kishida, T. Takenobu, Y. Iwasa, M. Shiraishi, M. Ata, and H. Okamoto

Physical Review Letters 94 巻頁： 047404-1 － 047404-4 2005年2月

記述言語：英語掲載種別：研究論文（学術雑誌）

We measured third-order nonlinear susceptibility spectra in semiconducting single-walled carbon
nanotubes (SWNTs) by the Z-scan method. Im chi^(3) is remarkably enhanced under resonant excitation to
the lowest interband transition, reaching 4×10^-6 esu and 1×10^-7 esu in SWNTs grown by the laser
ablation and HiPco methods, respectively. A comparison of the transient absorption changes evaluated by
degenerate and nondegenerate pump-probe measurements suggests that the resonant enhancement of
Im chi(3) is dominated by a coherent process rather than by saturation of absorption.

DOI： 10.1103/PhysRevLett.94.047404

Photoinduced phase transition in tetrathiafulvalene-p-chloranil observed in femtosecond reflection spectroscopy 査読有り

H. Okamoto, Y. Ishige, S. Tanaka, H. Kishida, S. Iwai, Y. Tokura

Physical Review B 70 巻頁： 165202-1 - 126502-18 2004年10月

記述言語：英語掲載種別：研究論文（学術雑誌）

Photoinduced transitions from ionic sId to neutral sNd and neutral sNd to ionic sId phases in an organic charge
transfer (CT) complex, tetrathiafulvalene-p-chloranil (TTF-CA), were investigated by femtosecond pumpprobe
reflection spectroscopy. Transient reflectivity changes of the intramolecular transition band of TTF
sensitive to the degree of CT between a donor molecule of TTF and an acceptor molecule of CA are measured
as a function of excitation energy, excitation density, and temperature. By adopting the multilayer model for the
analysis of the obtained transient reflectivity spectra, we have derived the time characteristics of amounts and
spatial distributions of photoinduced N sId states in the I sNd phase. The results reveal that the I to N sINd
transition induced by the resonant excitation of the CT band at 4 K is composed of three processes; (1)
formation of a confined one-dimensional (1D) N domain, that is, a sequence of D0A0 pairs, just after the
photoexcitation, (2) multiplication of the 1D N domains to the semimacroscopic N states up to 20 ps within the
absorption depth of the excitation light, and (3) proceeding of the IN transition along the direction normal to
the sample surface. At 77 K near the NI transition temperature sTc=81 Kd, the size of the 1D N domain
initially produced is enlarged and its multiplication process is strongly enhanced. When the excitation energy
is increased, the initial photoproduct is changed from the confined 1D N domain to the positively and negatively
charged N states. The spatial size of the latter is considerably larger than that of the former, indicating
that the introduction of charge carriers makes the neighboring I state strongly unstable. The dynamics of the
photoinduced N to I sNId transition has also been investigated. The 1D I domains are initially produced by
lights, however, they decay within 20 ps even if the density of the I domains is increased. The results demonstrate
that there is a cle

DOI： 10.1103/PhysRevB.70.165202

Charge dynamics of Ca_2-xNa_xCuO₂Cl₂ as a correlated electron system with the ideal tetragonal lattice 査読有り

K. Waku, T. Katsufuji, Y. Kohsaka, T. Sasagawa, H. Takagi, H. Kishida, H. Okamoto, M. Azuma, M. Takano

Physical Review B 70 巻頁： 134501-1 － 134501-8 2004年10月

記述言語：英語掲載種別：研究論文（学術雑誌）

We report the reflectivity and the resistivity measurement of Ca2-xNaxCuO2Cl2 (CNCOC), which has a
single-CuO2-plane lattice with no orthorhombic distortion. The doping dependence of the in-plane optical
conductivity spectra for CNCOC is qualitatively the same to those of other cuprates, but a slight difference
between CNCOC and LSCO, i.e., the absence of the 1.5 eV peak in CNCOC, can be attributed to the smaller
charge-stripe instability in CNCOC. The temperature dependence of the optical conductivity spectra of CNCOC
has been analyzed both by the two-component model (Drude1Lorentzian) and by the one-component
model (extended-Drude analysis). The latter analysis gives a universal trend of the scattering rate Gsvd with
doping. It was also found that Gsvd shows a saturation behavior at high frequencies, whose origin is the same
as that of resistivity saturation at high temperatures.

DOI： 10.1103/PhysRevB.70.134501

Third-order nonlinear susceptibility spectra of CuO chain compounds investigated by the Z-scan method 査読有り

A. Maeda, M. Ono, H. Kishida, T. Manako, A. Sawa, M. Kawasaki, Y. Tokura, H. Okamoto

Physical Review B 70 巻頁： 125117-1- 125117-7 2004年9月

Third-order optical nonlinearity in charge-transfer-type conjugated polymers 査読有り

H. Kishida, K. Hirota. T. Wakabayashi, B. L. Lee, H. Kokubo, T. Yamamoto, H. Okamoto

Physical Review B 70 巻頁： 115205-1 – 115205-5 2004年9月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）

We have studied third-order nonlinear optical (NLO) properties of charge-transfer- (CT) type conjugated
copolymer composed of an electron-donating molecule, thiophene, and electron-accepting one, quinoxaline,
using the electroabsorption, two-photon absorption, and third-harmonic generation spectroscopies. The analyses
of the obtained nonlinear optical spectra reveal that the CT character of the excited states leads to small
oscillator strength of linear absorption but large third-order nonlinear susceptibility, resulting in the strong
enhancement of figure of merit for NLO devices.

DOI： 10.1103/PhysRevB.70.115205

Linear and nonlinear optical properties of one-dimensional Mott insulators consisting of Ni-halogen chain and CuO-chain compounds 査読有り

M.Ono, K. Miura, A. Maeda, H. Matsuzaki, H. Kishida, Y. Taguchi, Y. Tokura, M. Yamashita, H. Okamoto

Physical Review B 70 巻頁： 085101-1 - 085101-20 2004年8月

Tuning the electronic structure from charge-transfer insulator to Mott-Hubbard and Peierls insulators in one-dimensional halogen-bridged mixed-metal compounds 査読有り

H. Matsuzaki, K. Iwano, T. Aizawa, M. Ono, H. Kishida, M. Yamashita, and H. Okamoto

Physical Review B 70 巻頁： 035204-1 – 035204-6 2004年7月

Visualization of local valence structures in quasi-one-dimensional halogen-bridged complexes [Ni_1-xPd_x(chxn)₂Br]Br₂ by STM 査読有り

S.Takaishi, H. Miyasaka, K. Sugiura, M. Yamashita, H. Matsuzaki, H. Kishida, H. Okamoto, H. Tanaka, K. Marumoto, H. Ito, S. Kuroda, T. Takami

Angewandte Chemie International Edition 43 巻頁： 3171-3175 2004年6月

Third-harmonic generation in CT-type conjugated polymers 査読有り

H. Kishida, H. Okamoto, B. L. Lee, H. Kokubo, and T. Yamamoto

Transaction of the Materials Research Society of Japan 29 巻 ( 3 ) 頁： 981-984 2004年5月

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