研究者詳細 - 近藤　隆祐

論文 - 近藤　隆祐

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Structural and Superconducting Properties of Bi₂Rh₃(Se_1–xS_x)₂ (x = 0–1.0) 査読

63 ( 45 ) 21531 - 21540 2024年10月

Control of Polar/Antipolar Layered Organic Semiconductors by the Odd‐Even Effect of Alkyl Chain

Satoru Inoue, Toshiki Higashino, Kiyoshi Nikaido, Ryo Miyata, Satoshi Matsuoka, Mutsuo Tanaka, Seiji Tsuzuki, Sachio Horiuchi, Ryusuke Kondo, Ryoko Sagayama, Reiji Kumai, Daiki Sekine, Takayoshi Koyanagi, Masakazu Matsubara, Tatsuo Hasegawa

Advanced Science 11 ( 13 ) 2024年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Wiley

Abstract

Some rodlike organic molecules exhibit exceptionally high layered crystallinity when composed of a link between π‐conjugated backbone (head) and alkyl chain (tail). These molecules are aligned side‐by‐side unidirectionally to form self‐organized polar monomolecular layers, providing promising 2D materials and devices. However, their interlayer stacking arrangements have never been tunable, preventing the unidirectional arrangements of molecules in whole crystals. Here, it is demonstrated that polar/antipolar interlayer stacking can be systematically controlled by the alkyl carbon number n, when the molecules are designed to involve effectively weakened head‐to‐head affinity. They exhibit remarkable odd–even effect in the interlayer stacking: alternating head‐to‐head and tail‐to‐tail (antipolar) arrangement in odd‐n crystals, and uniform head‐to‐tail (polar) arrangement in even‐n crystals. The films show excellent field‐effect transistor characteristics presenting unique polar/antipolar dependence and considerably improved subthreshold swing in the polar films. Additionally, the polar films present enhanced second‐order nonlinear optical response along normal to the film plane. These findings are key for creating polarity‐controlled optoelectronic materials and devices.

DOI： 10.1002/advs.202308270

Pressure Dependence of the Structural and Superconducting Properties of the Bi-Based Superconductor Bi₂Pd₃Se₂ 査読

Zhiyan Zhang, Mitsuki Ikeda, Masaki Utsumi, Yuki Yamamoto, Hidenori Goto, Ritsuko Eguchi, Yen-Fa Liao, Hirofumi Ishii, Yasuhiro Takabayashi, Koichi Hayashi, Ryusuke Kondo, Tatsuo C. Kobayashi, Yoshihiro Kubozono

Inorganic Chemistry 63 ( 5 ) 2553 - 2561 2024年1月

Temperature-induced transformation between layered herringbone polymorphs in molecular bilayer organic semiconductors 査読

Shunto Arai, Satoru Inoue, Mutsuo Tanaka, Seiji Tsuzuki, Ryusuke Kondo, Reiji Kumai, Tatsuo Hasegawa

Physical Review Materials 7 ( 2 ) 2023年2月

Highly stable and isomorphic donor–acceptor stacking in a family of n-type organic semiconductors of BTBT–TCNQ derivatives 査読

Satoshi Matsuoka, Kazuma Ogawa, Ryota Ono, Kiyoshi Nikaido, Satoru Inoue, Toshiki Higashino, Mutsuo Tanaka, Jun'ya Tsutsumi, Ryusuke Kondo, Reiji Kumai, Seiji Tsuzuki, Shunto Arai, Tatsuo Hasegawa

Journal of Materials Chemistry C 10 ( 43 ) 16471 - 16479 2022年

Spin Dynamics in the Mixed Stack Charge Transfer Complex, (BEDO-TTF)(Cl2TCNQ) 査読

Ko-ichi Hiraki, Masashi Takahashi, Toshihiro Takahashi, Tatsuo Hasegawa, Ryusuke Kondo, Seiichi Kagoshima

Journal of the Physical Society of Japan 89 ( 7 ) 074706 - 074706 2020年7月

Multiple charge density waves compete in ternary rare-earth nickel carbides,RNiC2(R: Y, Dy, Ho, and Er) 査読

H. Maeda, Ryusuke Kondo, Y. Nogami

PHYSICAL REVIEW B 100 104107 2019年9月

Possible charge order structure of stoichiometric YbFe2O4 査読

Kosuke Fujiwara, Tomoyuki Karasudani, Mamoru Fukunaga, Hiroyuki Kobayashi, Jun Kano, Pierre-Eymeric Janolin, Jean-Michel Kiat, Yoshio Nogami, Ryusuke Kondo, Naoshi Ikeda

FERROELECTRICS 512 ( 1 ) 85 - 91 2017年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：TAYLOR & FRANCIS LTD

We report a possible charge ordering model of triangular mixed valence material YbFe2O4. It was found that a crystal synthesized with high stoichiometry on iron vacancy shows new and simple extinction rule in the superlattice reflections. The Laue class of the diffraction signal is expressed as 2/m. With the consideration of the charge neutrality and the superlattice signal of (1/3 1/3 0), we derived 5 possible charge ordering models of this material.

DOI： 10.1080/00150193.2017.1349945

Interplay of Charge-Density Wave and Magnetic Order in Ternary Rare-Earth Nickel Carbides, RNiC2 (R = Pr and Nd) 査読

Nobuki Yamamoto, Ryusuke Kondo, Hiroyuki Maeda, Yoshio Nogami

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 82 ( 12 ) 2013年12月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOC JAPAN

The electrical and structural properties of NdNiC2 and PrNiC2 are examined in single-crystalline samples in order to investigate the interplay of charge-density wave (CDW) and magnetic order in ternary rare-earth nickel carbides, RNiC2, where R is a rare-earth element. PrNiC2 (no magnetic order down to 1.5 K) and NdNiC2 [antiferromagnetic (AF) transition at 17.2 K] show resistance anomalies at 89 and 121 K, respectively, which are revealed to be CDW transitions by observing X-ray satellite reflections. NdNiC2 also shows a gradual decrease in both resistivity and CDW amplitude below the Neel temperature. In the AF phase, the magnetoresistance sharply decreases where a ferromagnetic (FM) order occurs, which is realized above the spin-flop magnetic field. These results clearly suggest that the relationships between CDW and magnetic order in RNiC2 depend on whether the magnetic order is AF or FM.

DOI： 10.7566/JPSJ.82.123701

Reproducible synthetic method for the topological superconductor CuxBi2Se3 査読

Ryusuke Kondo, Taiki Yoshinaka, Yoshinori Imai, Atsutaka Maeda

Journal of the Physical Society of Japan 82 ( 6 ) 2013年6月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）

We report a reproducible synthetic method for superconducting Cu-intercalated Bi2Se3 by an improved melt growth method. Avoiding the production of Cu2Se, which has a higher melting point than that of Bi2Se3, and quenching Cu- Bi-Se mixtures at the liquid phase are keys to obtaining good superconducting samples in a reproducible manner. © 2013 The Physical Society of Japan.

DOI： 10.7566/JPSJ.82.063702

Superconductivity at 5.4 K in beta-Bi2Pd 査読

Yoshinori Imai, Fuyuki Nabeshima, Taiki Yoshinaka, Kosuke Miyatani, Ryusuke Kondo, Seiki Komiya, Ichiro Tsukada, Atsutaka Maeda

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 81 ( 11 ) 2012年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOC JAPAN

We investigate bulk superconductivity in a high-quality single crystal of Bi2Pd (beta-Bi2Pd; space group: I4/mmm) with a superconducting transition temperature of 5.4 K, by exploring its electrical resistivity, magnetic susceptibility, and specific heat. The temperature dependence of the electrical resistivity shows convex-upward behavior at temperatures greater than 40-50 K, which can be explained using a parallel-resistor model. In addition, the temperature dependences of the upper critical magnetic field and the specific heat suggest that beta-Bi2Pd is a multiple-band/multiple-gap superconductor.

DOI： 10.1143/JPSJ.81.113708

Ultrafast photo-induced insulator-to-metal transition in the spin density wave system of (TMTSF)(2)PF6 査読

Shinichi Watanabe, Ryusuke Kondo, Seiichi Kagoshima, Ryo Shimano

PHYSICA B-CONDENSED MATTER 405 ( 11 ) S360 - S362 2010年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

We demonstrate a photo-induced insulator-to-metal (I-M) transition in an organic linear chain compound (TMTSF)(2)PF6 [bis-(tetramethyl-tetraselenafulvalene)hexafluorophosphate] in the spin-density-wave (SOW) ground state by optical pump and terahertz probe experiments We observe the collapse of SOW gap in the optical conductivity spectrum at 3 ps after the photo-excitation indicating the ultrafast I-M transition in the SOW system Temporal evolution of the terahertz reflectivity change shows that the photo-induced metallic state sustains longer than 400 Ps (C) 2009 Elsevier B V All rights reserved

DOI： 10.1016/j.physb.2009.10.063

Electronic states of organic quasi-two dimensional conductor beta ''-(DODHT)(2)PF6 center dot Charge ordering and superconductivity 査読

M. Higa, R. Kondo, A. Murata, S. Kagoshima, H. Nishikawa, K. Yakushi

PHYSICA B-CONDENSED MATTER 405 ( 11 ) S172 - S175 2010年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

In the title compound we made X-ray satellite reflection measurements up to 0 7 GPa and angle-dependent magnetoresistance (AMR) measurements at 1 9 GPa The purpose of the study is to clarify (1) how large the temperature-pressure regime is for the long-range charge ordering (CO) (2) whether or not the high pressure regime for the superconductivity is really a metallic state and (3) what the electronic properties are in the intermediate pressure regime between the long-range CO and the superconducting states The long-range CO was found to be stable up to 0 7 GPa and its temperature-pressure regime coincides with that expected from transport measurements AMR at 1 9 GPa 1 4K and 12T suggests the presence of Fermi surfaces consistent with band calculations based on X-ray structural analyses at room temperature and the same pressure Raman studies by one of the authors (K Y) suggest the presence of metallic state in the intermediate pressure regime where the resistance shows apparently insulating properties Discussion is made on the role of the charge-degree of freedom in causing the superconductivity (C) 2009 Elsevier B V All rights reserved

DOI： 10.1016/j.physb.2009.11.092

Interplay of charge-density waves and superconductivity in the organic conductor β"-(BEDT-TTF)2AuBr2 査読

Ryusuke Kondo, Momoka Higa, Seiichi Kagoshima, Noriaki Hanasaki, Yoshio Nogami, Hiroyuki Nishikawa

Phys. Rev. B 81 ( 2 ) 024519 2010年1月

Observation of ultrafast photoinduced closing and recovery of the spin-density-wave gap in (TMTSF)(2)PF6 査読

Shinichi Watanabe, Ryusuke Kondo, Seiichi Kagoshima, Ryo Shimano

PHYSICAL REVIEW B 80 ( 22 ) 2009年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSICAL SOC

Photoexcited dynamics of a spin-density-wave (SDW) state in an organic linear-chain compound bis-(tetramethyl-tetraselenafulvalene)hexafluorophosphate, (TMTSF)(2)PF6, is investigated by optical pump and terahertz probe experiments. After the ultrashort laser-pulse excitation, a sudden closing followed by a recovery of the SDW gap is clearly observed in the far-infrared spectrum. The recovery time is found to diverge toward the phase-transition temperature, T-SDW, while the gap remains open at T-SDW. The observed critical slowing down behavior is interpreted in terms of three-dimensional fluctuation which enlarges near the phase-transition temperature.

DOI： 10.1103/PhysRevB.80.220408

Effects of Hydrostatic Pressure and Uniaxial Strain on Spin-Peierls Transition in an Organic Radical Magnet, BBDTA center dot InCl4 査読

Masaki Mito, Seiichiro Kawagoe, Hiroyuki Deguchi, Seishi Takagi, Wataru Fujita, Kunio Awaga, Ryusuke Kondo, Seiichi Kagoshima

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 78 ( 12 ) 2009年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOC JAPAN

We investigated the effects of hydrostatic pressure and uniaxial strain on the spin-Peierls (SP) transition of an organic radical magnet, benzo[1,2-d:4,5-d']bis[1,3,2]dithiazole(BBDTA)center dot InCl4. It has a one-dimensional coordination polymer structure along its c-axis and its SP transition occurs at 108 K. The SP transition temperature T-SP decreased to 99K at a hydrostatic pressure of 10 kbar, while it increased to 132 K at a uniaxial strain along the c-axis of 8 kbar. The pressure dependences of T-SP under these two conditions were discussed by evaluatingg two parameters, namely, the intrachain interaction 2J/k(B) and the effective spin-lattice coupling parameter eta, that are related to T-SP by the equation T-SP = 1.6 eta J/k(B). Under ambient pressure, the a- and c-axes of this material shortened monotonically with decreasing temperature, while the b-axis elongated below T-SP. In this study, we found the correlation between eta and the change in the lattice constant b. 2J/k(B) increased with increasing hydrostatic pressure and uniaxial strain, suggesting that the contraction along the c-axis does not depend on the manner of pressurization. From the evaluation of eta, the observed variation in T-SP is explained by the difference between the changes in b under the two pressurization conditions.

DOI： 10.1143/JPSJ.78.124705

Crystal and Electronic Structures of the Quasi-Two-Dimensional Organic Conductor alpha-(BEDT-TTF)(2)I-3 and Its Selenium Analogue alpha-(BEDT-TSeF)(2)I-3 under Hydrostatic Pressure at Room Temperature 査読

Ryusuke Kondo, Seiichi Kagoshima, Naoya Tajima, Reizo Kato

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 78 ( 11 ) 2009年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOC JAPAN

We perform crystal structure analyses of the organic conductor alpha-(BEDT-TTF)(2)I-3 [where BEDT-TTF denotes bis(ethylene)dithiotetrathiafulvalene] and its selenium analogue alpha-(BEDT-TSeF)(2)I-3 [where BEDT-TSeF denotes bis(ethylene)dithiotetraselenafulvalene] at room temperature under hydrostatic pressure, where they are expected to have zero-gap points at the Fermi level with a Dirac-cone-type dispersion for a massless particle. We calculate the electronic band structures using a combination of the extended Huckel molecular orbital calculation based on the obtained crystal structures and the tight-binding band structure calculation. We find that I) the obtained Fermi surfaces of both salts under hydrostatic pressure are simply larger than those at ambient pressure owing to an increase in overlap integrals caused by the pressure, and II) electronic structures having zero-gap points with a Dirac-cone-type dispersion at the Fermi level are realized only in alpha-(BEDT-TTF)(2)I-3 by the introduction of suitable site potentials in wide parameter areas. These results suggest that, to realize such a unique electronic structure in this class of materials, some mechanisms are needed to effectively give the site potentials employed in this study. Examples are electronic correlation effects and I-3 anion potentials.

DOI： 10.1143/JPSJ.78.114714

Ultrafast terahertz probe of spin-density wave dynamics in organic conductor (TMTSF)(2)PF6 査読

S. Watanabe, R. Kondo, S. Kagoshima, R. Shimano

2009 CONFERENCE ON LASERS AND ELECTRO-OPTICS AND QUANTUM ELECTRONICS AND LASER SCIENCE CONFERENCE (CLEO/QELS 2009), VOLS 1-5 2993 - + 2009年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：IEEE

Photo-induced terahertz reflectivity change of the spin-density wave (SDW) gap in (TMTSF)(2)PF6 is observed. We find an ultrafast (similar to ps) increase of terahertz conductivity indicating a destabilization of the SDW states by a weak photo-excitation. (C) 2009 Optical Society of America

Spin-density-wave gap in (TMTSF)(2)PF6 probed by reflection-type terahertz time-domain spectroscopy 査読

Shinichi Watanabe, Ryusuke Kondo, Seiichi Kagoshima, Ryo Shimano

PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS 245 ( 12 ) 2688 - 2691 2008年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：WILEY-BLACKWELL

We report on a development of the reflection-type terahertz time-domain spectroscopy system and apply it to determine the conductivity spectra of the spin density wave (SDW) ground states in (TMTSF)(2)PF6. We take special care over optimizing the spatial resolution of the measurement system in order to investigate the tiny sample and also for correcting the phase error of the measurement. We observe a distinct reduction of the optical conductivity below similar to 65 cm(-1), which is a clear indication of SDW gap formation with metal-insulator transition. (c) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

DOI： 10.1002/pssb.200879900

Charge ordered insulating phases of DODHT salts with octahedral anions and a new radical salt, β″-(DODHT)2TaF6

H Nishikawa, H Oshio, M Higa, R Kondo, S Kagoshima, A Nakao, H Sawa, S Yasuzuka, K Murata

Journal of Physics: Conference Series 132 012023 - 012023 2008年10月

Hump like resistance anomaly in organic conductor β"-(BEDT-TTF)(2)CsCd(SCN)(4) 査読

Kondo Ryusuke, Otsuji Jun, Kagoshima Seiichi, Nogami Yoshio

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 77 ( 6 ) 2008年6月

Charge ordered metal and pressure-induced superconductivity in the two-dimensional organic conductor beta-(DODHT)(2)PF(6) 査読

Akito Kobayashi, Yoshikazu Suzumura, Momoka Higa, Ryusuke Kondo, Seiichi Kagoshima, Hiroyuki Nishikawa

JOURNAL OF PHYSICS-CONDENSED MATTER 20 ( 12 ) 2008年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：IOP PUBLISHING LTD

The superconductivity in a quasi-two-dimensional organic conductor, beta"-(DODHT)(2)PF(6) salt, which is expected to appear after the melting of a charge ordering (CO) state, has been examined using an extended Hubbard model with anisotropy for both the transfer energies and the nearest-neighbor repulsive interactions between the DODHT molecules. The fluctuation is treated by the random phase approximation based on mean-field calculation of the CO. When pressure is applied, an insulating state with CO (COI) changes into a metallic state with weakened CO (COM) at an intermediate pressure, and a normal state without CO emerges at higher pressures. For the COM state at intermediate pressure, the COI state and the normal state also exist as metastable states, and their free energies are nearly the same within a narrow energy range of 10(-3) eV. Thus these three states may coexist with each other by forming a phase separation at finite temperature. We find that the spin fluctuation around such a mean-field COM state gives rise to a superconducting state with a full gap. Further, we suggest that d-wave superconductivity mediated by the charge fluctuation occurs in the normal state with a quasi-one-dimensional Fermi surface when the nearest-neighbor interaction becomes as large as the on-site interaction.

DOI： 10.1088/0953-8984/20/12/125205

Development of uniaxial elongation method and its application to low dimensional conductors 査読

Hiroki Kowada, Ryusuke Kondo, Seiichi Kagoshima

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 76 ( 11 ) 2007年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOC JAPAN

We developed the uniaxial elongation method to elongate a soft crystalline sample along one desired direction. An epoxy rod which contains a sample passes through a stainless steel ring along its diameter and is fixed to the ring. The external force is applied to the ring along the direction perpendicular to the epoxy rod to deform the ring and elongate the epoxy rod, leading to the elongation of the sample in the rod. We verify this method by using a strain gauge instead of a sample. The results of resistance measurements of two kinds of quasi-one-dimensional conductors, NbSe3 and (TMTSF)(2)ClO4(TMTSF denotes tetramethyltetraselenafulvalene.), are also presented as the examples of this experimental technique.

DOI： 10.1143/JPSJ.76.114710

Structural studies of pressure-induced organic superconductor beta ''-(DODHT)(2)PF6 having charge-ordering phase at ambient pressure 査読

Momoka Higa, Ryusuke Kondo, Seiichi Kagoshima, Hiroyuki Nshikawa

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 76 ( 3 ) 2007年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOC JAPAN

We performed the crystal structure analyses of the pressure-induced organic superconductor ss"-(DODHT)(2)PF6 (DODHT denotes (1,4-dioxane-2,3-diyldithio)dihydrotetrathiafulvalene) at the hydrostatic pressures of 0.75GPa and 1.9GPa in order to investigate the key parameter for inducing the superconductivity. At ambient pressure, ss"-(DODHT)(2)PF6 undergoes an insulator-to-insulator transition at 255 K accompanied by charge ordering. By applying pressure, this charge-ordering transition is suppressed and superconductivity is generated at around 3 K above 1.32 GPa. Using the obtained atomic coordinates, we estimated the transfer integrals t and intermolecular nearest-neighbor Coulomb interaction energies V between conduction electrons and found that one of V/vertical bar t vertical bar ratios perpendicular to charge-ordering stripes plays an important role in suppressing the charge-ordering phase.

DOI： 10.1143/JPSJ.76.034709

A possible internal deformation of the charge ordering and its meta-stability in the organic conductor theta-(BEDT-TTF)(2)CsZn(SCN)(4) 査読

Ryusuke Kondo, Mornoka Higa, Seiichi Kagoshima

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 76 ( 3 ) 2007年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOC JAPAN

Non-ohmic transport was studied by pulse method in the charge-ordered state of the organic conductor theta-(BEDT-TTF)(2)CsZn(SCN)(4) as controlling the electronic state by uniaxial strain method. It was discovered that the non-ohmic conduction under high electric fields lead to the meta-stable state with a structural modification, where the ohmic resistance was reduced to be smaller than the original. The response of the CO state to pulsed electric fields suggested a possible internal deformation of the ordered charge's lattice.

DOI： 10.1143/JPSJ.76.033703

Anisotropic superconducting transition in beta ''-(DODHT)(2)PF6 査読

Momoka Higa, Ryusuke Kondo, Seiichi Kagoshima, Hiroyuki Nishikawa

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 76 186 - 187 2007年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOC JAPAN

We report unique resistance behavior around the superconducting transition of a quasi-two-dimensional organic superconductor, beta '''-(DODHT)(2)PF6 [DODHT = (1,4-dioxane-2,3-diyldithio)dihydrotetrathiafulvalene]. When the superconductivity appears, the interlayer resistance begins to decrease at a temperature higher than that for the intralayer resistance. Both resistances show a step-like decrease toward zero resistance. These unique phenomena are possibly related to the unique structural properties of the salt.

DOI： 10.1143/JPSJS.76SA.186

Ultrahigh-pressure effects in metallo-organics 査読

Seiichi Kagoshima, Ryusuke Kondo, Nobuyuki Matsushita, Momoka Higa, Sergey V. Ovsyannikov, Nadezhda A. Shaydarova, Vladimir V. Shchennikov, Andrey Y. Manakov, Anna Y. Likhacheva

PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS 244 ( 1 ) 418 - 423 2007年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：WILEY-V C H VERLAG GMBH

The results are reported of the pressure (P) dependence of the electrical resistance (R), the thermoelectric power (Seebeck effect) (S), and compressibility as well as the time dependence of R at fixed P up to 20 GPa for four metallo-organics based on the BEDT-TTF (bisethylenedithiolo-tetrathiofulvalene) group, theta-(BEDT-TTF)(2)CsZn(SCN)(4), alpha-(BEDT-TTF)(2)I-3, beta'-(BEDT-TTF)(2)PF6, and (BEDT-TTF)-TCNQ. X-ray powder and single-crystal diffraction studies were also made on theta-(BEDT-TTF)(2)CsZn(SCN)(4) at high pressures up to P similar to 10 GPa. The R values of all the crystals decreased with pressure up to P similar to 3-5 GPa (low-pressure regime), and then the sign of dR/dP inverted (high-pressure regime). From the investigation of the mechanical and structural properties, these materials were found to have a large compressibility in the low-pressure regime, and a small one in the high-pressure region. In theta-(BEDT-TTF)(2)CsZn(SCN)(4) we observed pressure-induced reversible degradation (amorphization) in structure without a solid-phase reaction. (C) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DOI： 10.1002/pssb.200672530

High-pressure research in organic conductors 査読

Keizo Murata, Seiichi Kagoshima, Syuma Yasuzuka, Harukazu Yoshino, Ryusuke Kondo

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 75 ( 5 ) 2006年5月

記述言語：英語出版者・発行元：PHYSICAL SOC JAPAN

High-pressure studies on organic conductors and superconductors are reviewed. It is stressed that almost all the organic conductors are studied by means of high pressures, but the role or meaning of pressure effect has been dependent on the salts and physics of interests. In organic molecular crystals, many intriguing physical phenomena such as the appearance of charge- and spin-density-waves, superconductivity, Mott insulator and charge ordering have been found. The application of hydrostatic and uniaxial pressures plays an essential role for understanding the nature of these electronic states, for guiding the material design, and for creating the unexpected quantum states as well as high-T-c superconductivities. This review includes the history, pressure techniques, and works under conventional pressures of up to 1.5 GPa, ultra-high pressures up to 10 GPa as well as uniaxial pressure, but the topics which are dealt with in this same special issue are not covered.

DOI： 10.1143/JPSJ.75.051015

A one-dimensional coordination polymer, BBDTA center dot InCl4: Possible spin-Peierls transition with high critical temperature of 108 K 査読

Wataru Fujita, Kunio Awaga, Ryusuke Kondo, Seiichi Kagoshima

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 128 ( 18 ) 6016 - 6017 2006年5月

Electrical and Structural Properties of θ-type BEDT-TTF Organic Conductors under Uniaxial Strain 査読

R. Kondo, M. Higa, S. Kagoshima, H. Hoshino, T. Mori, H. Mori

Journal of the Physical Society of Japan 75 ( 4 ) 044716 2006年4月

Superconducting and charge ordering phases of two-dimensional organic conductors 査読

R. Kondo, M. Higa, S. Kagoshima

JOURNAL OF LOW TEMPERATURE PHYSICS 142 ( 3-4 ) 535 - 538 2006年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：SPRINGER/PLENUM PUBLISHERS

In order to investigate relationships between superconducting phase and charge ordered one, the uniaxial strain method is applied to the superconducting salt alpha-(BEDT-TTF)(2)NH4Hg(SCN)(4) and the organic conductor alpha-(BEDT-TTF)(2)CSCd(SCN)(4). Both salts preserve metallic states under a-axial strain and show insulating behaviours under c-axial strain. These results suggest that i) c-axial strain controls the electronic properties of the a-type salts, and ii) the insulating state in the vicinity of the superconducting phase of alpha-(BEDT-TTF)(2)NH4Hg(SCN)(4) is a charge ordered phase, as expected from the comparison in the lattice parameters with the charge ordered salt theta-(BEDT-TTF)(2)RbZn(SCN)(4).

Magnetic correlation in BETS2(Cl(2)TCNQ) 査読

Y. Takano, K. Hiraki, T. Takahashi, R. Kondo, S. Kagoshima, T. Hasegawa, T. Mocihda, Y. Iwasa

JOURNAL OF LOW TEMPERATURE PHYSICS 142 ( 3-4 ) 647 - 650 2006年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：SPRINGER/PLENUM PUBLISHERS

We carried out Se-77 NMR measurements on BETS2(Cl(2)TCNQ) under pressure in order to investigate the magnetic properties of the insulating state which appears above 0.6 GPa. The relaxation rate 1/T-1 at 0.7 GPa shows small peak-like anomaly at 20 K, indicating a spin density wave transition as observed in BETS2(Br(2)TCNQ).

DOI： 10.1007/s10909-006-9201-0

Ultra high pressure application to organic conductors 査読

S. Kagoshima, R. Kondo, N. Matsushita, S. V. Ovsyannikov, N. A. Shaidarova, V. V. Shchennikov

JOURNAL OF LOW TEMPERATURE PHYSICS 142 ( 3-4 ) 409 - 412 2006年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：SPRINGER/PLENUM PUBLISHERS

Under pressures as high as 20 GPa at room temperature the electronic and structural properties of organic conductors were measured to search for interesting pressure regimes where novel electronic states were expected. Thermopower, two-probe electrical resistance and contraction of sample's volume were measured on the organic conductors: theta-(BEDT-TTF)(2)CsZn(SCN)(4), alpha-(BEDT-TTF)(2)I-3, (BEDT-TTF)(2)PF6 and (BEDT-TTF)-TCNQ. All the materials exhibited a positive thermopower of the order of 10 mu V/K. At about 4-7 GPa (crossover pressure P-x) sharp changes were found in the pressure dependence of electronic and mechanical properties of all the substances under consideration related probably to the structural changes under pressure.

DOI： 10.1007/s10909-006-9126-7

その他リンク： http://orcid.org/0000-0003-1022-430X

Charge ordered insulating state in DODHT salts 査読

H. Nishikawa, Y. Sato, T. Kodama, K. Kikuchi, I. Ikemoto, J. Yamada, H. Oshio, R. Kondo, S. Kagoshima

JOURNAL OF LOW TEMPERATURE PHYSICS 142 ( 3-4 ) 633 - 636 2006年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：SPRINGER/PLENUM PUBLISHERS

Radical salts based on DODHT [(1,4-dioxane-2,3-diyldithio)dihydrotetra-thialulvalene] are semiconductors at ambient pressure, but some salts (PF6, AsF6, and BF4 center dot H2O salts) exhibit supuerconducting transition under hydrostatic pressure. X-ray diffraction and magnetic susceptibility measurements at ambient pressure for PF6 salt revealed that the insulating phase at ambient pressure corresponds to a charge ordering (CO) state with stripe-type charge pattern. While the similar magnetic behavior was observed for BF4 salt, temperature dependence of magnetic susceptibility of AsF6 salt is quite different from those of the other salts.

DOI： 10.1007/s10909-006-9106-y

Magneto-transport properties in the density wave phase of beta ''-(BEDT-TTF)(2)CsCd(SCN)(4) 査読

R. Kondo, J. Otsuji, S. Kagoshima

YAMADA CONFERENCE LX ON RESEARCH IN HIGH MAGNETIC FIELDS 51 327 - + 2006年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：IOP PUBLISHING LTD

Magneto-transpon properties of the newly prepared layer-structured organic conductor beta"-(BEDT-TTF)(2)CsCd(SCN)(4) are investigated. Temperature dependence of the interlayer resistance without magnetic fields shows a hump-like anomaly between 32 K and 5 K at ambient pressure. Measurements of the Shubnikov-de Haas oscillations indicate that the electronic structure at low temperature is different from that calculated from the crystal structure at room temperature. Under magnetic fields parallel to the layer, magnetic field dependence of the interlayer resistance also shows a large dip-like anomaly below 32 K, where the hump-like anomaly starts to appear. We suggest that the hump-like anomaly of beta"-(BEDT-TTF)(2)CsCd(SCN)(4) is a density wave transition accompanied by nesting of its one dimensional Fermi surfaces, and that the dip-like anomaly in the magneto-resistance is ascribed to magnetic field dependence of the interlayer hopping of electrons.

DOI： 10.1088/1742-6596/51/1/076

Structural and electronic properties of a new molecular conductor, alpha-(BEDT-TTF)(2)CsCd(SCN)(4) 査読

R Kondo, M Higa, S Kagoshima

SOLID STATE COMMUNICATIONS 137 ( 12 ) 637 - 640 2006年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD

Structural and electronic properties of a new BEDT-TTF based radical cation salt, alpha-(BEDT-TTF)(2)CsCd(SCN)(4), are presented. In the measurements of the electrical resistivity and the magnetic susceptibility, this new a-type salt shows metallic behavior down to low temperature. Measurements of the resistivity under in-plane c-axial strain reveal a newly observed insulating phase, suggesting that alpha-(BEDT-TTF)(2)CsCd(SCN)(4) is placed near an insulating phase which might have close relationships with a superconducting phase realized in a-type salts. (c) 2006 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ssc.2006.01.025

Fermi surface study of organic conductors using a magnetooptical measurement under high magnetic fields 査読

M. Kimata, H. Ohta, K. Koyama, M. Motokawa, R. Kondo, S. Kagoshima, H. Tanaka, M. Tokumoto, H. Kobayashi, A. Kobayashi

YAMADA CONFERENCE LX ON RESEARCH IN HIGH MAGNETIC FIELDS 51 359 - + 2006年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：IOP PUBLISHING LTD

Magneto-optical measurements have been performed in organic conductors beta''-(BEDT-TTF)(2)CsCd(SCN), and lambda-(BETS)(2)FeCl4. Although the zero magnetic field ground state of beta"-(BEDT-TTF)(2)CsCd(SCN)(4) is considered as the density wave state, periodic orbit resonances (POR's) attributed to quasi-one-dimensional (Q1D) and quasi-two-dimensional (Q2D) Fermi surfaces (FS's) have been observed above 6 T. The existence of these FS's are predicted by the band calculation based on room temperature lattice parameters. This result may suggest the destruction of the density wave state at 6 T, and the primal metallic state revives in the high field phase above 6 T. In the case of lambda-(BETS)(2)FeCl4, large changes of the transmission intensity of electromagnetic waves around 10 T, which correspond to the insulator-metal transition, have been observed. However, no POR-like resonance has been observed. This may be due to the restriction of the observed frequency-field region.

DOI： 10.1088/1742-6596/51/1/084

Crystal structure analysis under uniaxial strain at low temperature using a unique design of four-axis x-ray diffractometer with a fixed sample 査読

R Kondo, S Kagoshima, J Harada

REVIEW OF SCIENTIFIC INSTRUMENTS 76 ( 9 ) 093902 2005年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER INST PHYSICS

For the purpose of crystal structure analysis under uniaxial strain at low temperatures, we developed a pressure cell for uniaxial compression and a unique design of an x-ray diffractometer wherein both the x-ray source and the detector are capable of two-axial rotation with a fixed sample. This arrangement is advantageous to crystal structure analyses under extreme conditions that require a large and heavy apparatus. Using the present diffractometer, we performed the crystal structure analyses of the organic conductor, alpha-(BEDT-TTF)(2)I-3 (BEDT-TTF denotes bis(ethylene)dithio-tetrathiafulvalene), under uniaxial strain and ambient pressure, and at room and low temperatures, and obtained results that were qualitatively consistent with those of resistivity measurements. (c) 2005 American Institute of Physics.

DOI： 10.1063/1.2001607

Charge ordering and pressure-induced superconductivity in "-(DODHT)2PF6. 査読

H. Nishikawa, Y. Sato, T. Kodama, K. Kikuchi, I. Ikemoto, J. Yamada, H. Oshio, R. Kondo, S. Kagoshima

Phys. Rev. B 72 ( 5 ) 052510 2005年8月

Molecular arrangement and electronic band structure of theta-(BEDT-TTF)(2)CsZn(SCN)(4) controlled by uniaxial compression 査読

R Kondo, M Higa, S Kagoshima, H Hoshino, T Mori, H Mori

CURRENT APPLIED PHYSICS 4 ( 5 ) 484 - 487 2004年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

Using the uniaxial strain method, the lattice parameters and the atomic positions of the quasi-two-dimensional organic conductor theta-(BEDT-TTF)(2)CsZn(SCN)(4) were measured at room temperature with piston pressures up to 10 kbar applied parallel to the c-axis in the conducting plane. The lattice parameter c was predominantly reduced with increasing the piston pressure although a small Poisson's effect occurred in the parameter a. Band calculation showed that the transfer integrals under the uniaxial compression by the piston pressure of 10 kbar became similar to those of theta-(BEDT-TTF)(2) RbZn(SCN)(4). This result is consistent with that of transport measurements reported already and suggests that a charge disproportionation, which has been observed in the RbZn-compound, occurs also in the present compound under the uniaxial compressive strain. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.cap.2004.01.004

Phase transition on (BEDO-TTF) (Cl(2)TCNQ): Spin dynamics observed by NMR measurements 査読

M Takahashi, K Hiraki, T Takahashi, T Hasegawa, R Kondo, S Kagoshima

JOURNAL DE PHYSIQUE IV 114 141 - 142 2004年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：E D P SCIENCES

C-13 NMR measurements were carried out to investigate the electronic state of Mixed-stack organic charge-transfer complex (BEDO-TTF)(Cl(2)TCNQ). From the remarkable temperature dependence of the central shift and relaxation rate, we have confirmed that the transition at 110 K is from paramagnetic to nonmagnetic spin-singlet phase.

DOI： 10.1051/jp4:2004114033

Crystal and electronic structures of alpha-(BEDT-TTF)(2)I-3 under uniaxial strains 査読

R Kondo, S Kagoshima

JOURNAL DE PHYSIQUE IV 114 523 - 525 2004年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：E D P SCIENCES

In order to investigate relationships between the crystal structure and electronic properties, crystal structure analyses of alpha-(BEDT-TTF)(2)I-3 were performed under in-plane uniaxial strains. It is known that, at ambient pressure, this salt has a semimetallic electronic structure having hole and electronic pockets, and undergoes a metal-insulator transition at 135 K due to a charge disproportionation on BEDT-TTF molecules. Present structure analyses showed that the sizes of both hole and electron like pockets on the Fermi surface rather decreased under a-axial strain, while those of hole ones increased under b-axial strain. These results are qualitatively consistent with observed behaviors of the metal-insulator transition under uniaxial strains.

DOI： 10.1051/jp4:2004114123

2k(F) transitions in a series of (DMET)(2)(X(1)X(2)TCNQ) (X(1), X(2)=Br, Cl, F, CH(3), H): Subsidiary lattice effect by anion radicals 査読

T Sato, T Hasegawa, T Akutagawa, T Nakamura, R Kondo

PHYSICAL REVIEW B 69 ( 7 ) 2004年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSICAL SOC

Structural and magnetic properties were investigated in a series of isomorphous 2:1 donor-acceptor-type organic charge-transfer (CT) complexes of (DMET)(2)(X(1)X(2)TCNQ) [DMET denotes dimethyl(ethylenedithio)diselenadithiafulvalene, TCNQ denotes tetracyanoquinodimethane, X(1),X(2)=Br,Cl,F,CH(3),H]. In these complexes, donors (D's) formed quasi-one-dimensional (Q1D) molecular stacks (D=+1/2), which were bridged with each other, by acceptor molecules whose molecular planes were parallel to the stacking axes. By the magnetic measurements, we found that the compounds could be classified into two groups in terms of the 2k(F) transitions of the donor stacks: two complexes exhibited the transitions at around room temperature, while the other two at lower temperature below 10 K. We discuss the origin of the difference in the observed 2k(F) transitions in terms of the subsidiary lattice effect by the acceptor molecules on the Q1D donor stacks.

DOI： 10.1103/PhysRevB.69.075103

2kF transitions in a series of (DMET)2(X 1X2TCNQ) (X1, X2=Br, Cl, F, CH 3, H): Subsidiary lattice effect by anion radicals

T. Sato, T. Hasegawa, T. Akutagawa, T. Nakamura, R. Kondo

Physical Review B - Condensed Matter and Materials Physics 69 ( 7 ) 751031 - 751035 2004年2月

記述言語：英語掲載種別：研究論文（学術雑誌）

Structural and magnetic properties were investigated in a series of isomorphous 2:1 donor-acceptor-type organic charge-transfer (CT) complexes of (DMET)2(X1X2TCNQ) [DMET denotes dimethyl(ethylenedithio)diselenadithiafulvalene, TCNQ denotes tetracyanoquinodimethane, X1, X2=Br, Cl,F,CH 3,H]. In these complexes, donors (D's) formed quasi-one-dimensional (Q1D) molecular stacks (D = + 1/2), which were bridged with each other, by acceptor molecules whose molecular planes were parallel to the stacking axes. By the magnetic measurements, we found that the compounds could be classified into two groups in terms of the 2kF transitions of the donor stacks: two complexes exhibited the transitions at around room temperature, while the other two at lower temperature below 10 K. We discuss the origin of the difference in the observed 2kF transitions in terms of the subsidiary lattice effect by the acceptor molecules on the Q1D donor stacks.

Crystal structure and electronic band structure of the organic superconductor alpha-(BEDT-TTF)(2)NH4Hg(SCN)(4) under uniaxial strain 査読

R Kondo, S Kagoshima, M Maesato

PHYSICAL REVIEW B 67 ( 13 ) 2003年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMERICAN PHYSICAL SOC

In order to investigate the relationship between the crystal structure and electronic properties, crystal structure analysis of the organic superconductor alpha-(BEDT-TTF)(2)NH4Hg(SCN)(4), where BEDT-TTF is the abbreviation of bis(ethylenedithio)tetrathiafulvalene, was performed under uniaxial compressive strain along each crystal axis. It was found that (i) almost ideal uniaxial strain was realized, that is, the unit cell was compressed only along the direction parallel to the external force; (ii) the calculated Fermi surface in the two-dimensional conducting layer was reduced along the k(c) axis and expanded along the k(a) axis under b(')- and c-axial strains, but vice versa under a-axial strain; and (iii) changes in the density of states at the Fermi level [DOS(E-F)] calculated from the obtained structures were qualitatively consistent with the observed change of the superconducting transition temperature.

DOI： 10.1103/PhysRevB.67.134519

Crystal structure and electronic band structure of the organic superconductor α-(BEDT-TTF)2NH4HG(SCN)4 under uniaxial strain 査読

Ryusuke Kondo, Seiichi Kagoshima, Mitsuhiko Maesato

Physical Review B - Condensed Matter and Materials Physics 67 ( 13 ) 1345191 - 1345196 2003年4月

記述言語：英語掲載種別：研究論文（学術雑誌）

In order to investigate the relationship between the crystal structure and electronic properties, crystal structure analysis of the organic superconductor α-(BEDT-TTF)2NH4Hg(SCN)4, where BEDT-TTF is the abbreviation of bis (ethylenedithio)tetrathiafulvalene, was performed under uniaxial compressive strain along each crystal axis. It was found that (i) almost ideal uniaxial strain was realized, that is, the unit cell was compressed only along the direction parallel to the external force
(ii) the calculated Fermi surface in the two-dimensional conducting layer was reduced along the kc axis and expanded along the ka axis under b'- and c-axial strains, but vice versa under a-axial strain
and (iii) changes in the density of states at the Fermi level [DOS(EF)] calculated from the obtained structures were qualitatively consistent with the observed change of the superconducting transition temperature.

Band structure control of organic superconductors by the uniaxial strain method 査読

S. Kagoshima, R. Kondo, M. Maesato

Synthetic Metals 137 ( 1-3 ) 1163 - 1165 2003年

Uniaxial strain study of electronic and crystal structures of organic conductors 査読

S. Kagoshima, R. Kondo, M. Chusho, M. Maesato, T. Mori, H. Mori, S. Tanaka

Synthetic Metals 133-134 145 - 146 2003年

Crystal and band structures of organic superconductor under the uniaxial strain 査読

R. Kondo, S. Kagoshima, M. Maesato

Physica C: Superconductivity and its Applications 388-389 601 - 602 2003年

Crystal structure of organic superconductor, α-(BEDT-TTF)₂NH₄Hg(SCN)₄, under the uniaxial strain 査読

R. Kondo, S. Kagoshima, M. Maesato

Synthetic Metals 133-134 137 - 139 2003年

Metal-insulator transition of donor-acceptor-type organic charge-transfer complex (BETS)2(Br2TCNQ): Site-selective NMR measurements 査読

K. Hiraki, S. Furuta, T. Takahashi, R. Kondo, S. Kagoshima, T. Hasegawa, T. Mochida, Y. Iwasa

Physical Review B - Condensed Matter and Materials Physics 66 ( 3 ) 351041 - 351046 2002年7月

記述言語：英語掲載種別：研究論文（学術雑誌）

The roles of donor layers and acceptor stacks in the electronic properties of the charge transfer complex, (BETS)2(Br2TCNQ) were investigated by means of site-selective NMR measurements. Line broadening of 77Se NMR indicating a magnetic ordering on the BETS site was observed at the metal-insulator transition temperature 12 K. This transition is caused by the spin-density-wave formation on the BETS layers. 13C NMR on the cyano carbon in the Br2TCNQ molecule confirms that a spin singlet formation starts to develop on the one dimensional Br2TCNQ columns below 170 K and its three dimensional ordering appears below 80 K. From the analysis of the NMR line shape and shift, magnetic susceptibility was decomposed into the contributions of the BETS and Br2TCNQ sites.

DOI： 10.1103/PhysRevB.66.035104

Metal-insulator transition of donor-acceptor-type organic charge-transfer complex (BETS)(2)(Br(2)TCNQ): Site-selective NMR measurements 査読

K Hiraki, S Furuta, T Takahashi, R Kondo, S Kagoshima, T Hasegawa, T Mochida, Y Iwasa

PHYSICAL REVIEW B 66 ( 3 ) 035104-1-035104-6 2002年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMERICAN PHYSICAL SOC

The roles of donor layers and acceptor stacks in the electronic properties of the charge transfer complex, (BETS)(2)(Br(2)TCNQ) were investigated by means of site-selective NMR measurements. Line broadening of Se-77 NMR indicating a magnetic ordering on the BETS site was observed at the metal-insulator transition temperature 12 K. This transition is caused by the spin-density-wave formation on the BETS layers. C-13 NMR on the cyano carbon in the Br(2)TCNQ molecule confirms that a spin singlet formation starts to develop on the one dimensional Br(2)TCNQ columns below 170 K and its three dimensional ordering appears below 80 K. From the analysis of the NMR line shape and shift, magnetic susceptibility was decomposed into the contributions of the BETS and Br(2)TCNQ sites.

DOI： 10.1103/PhysRevB.66.035104

Control of electronic properties of organic superconductors by uniaxial strain method 査読

S. Kagoshima, R. Kondo, T. Shibata, H. Hirai, M. Maesato, H. Hoshino, T. Mori, H. Mori, S. Tanaka

Molecular Crystals and Liquid Crystals Science and Technology Section A: Molecular Crystals and Liquid Crystals 380 77 - 84 2002年

Effects of uniaxial strain on α-(BEDT-TTF)₂MHg(SCN) ₄ [M=K, NH₄] 査読

M. Maesato, S. Kagoshima, R. Kondo, T. Shibata, H. Hirai

Molecular Crystals and Liquid Crystals Science and Technology Section A: Molecular Crystals and Liquid Crystals 376 195 - 200 2002年

Superconductivity and metal-insulator transition in twin-columnar organic superconductor, (BETS)(2)(X(2)TCNQ) [X=Cl, Br] 査読

R Kondo, T Hasegawa, T Mochida, S Kagoshima, Y Iwasa, K Hiraki, T Takahashi

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 70 ( 10 ) 3023 - 3030 2001年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOC JAPAN

Low-temperature electronic properties of the first all-organic donor-acceptor-type superconducting system, (BETS)(2)(X(2)TCNQ) [X=Cl, Br] under high pressure have been investigated by means of resistivity and H-1 NMR experiments. The crystal structure of this class of complexes is characterized by a twin-columnar structure of BETS without intra-columnar dimerization at room temperature. Pressure-temperature phase diagrams are established for these compounds, where the electronic ground status are spin-density-wave (SDW's) insulators, except a narrow, region of superconducting state in (BETS)(2)(Cl(2)TCNQ). A possible unified picture of the electronic states of the title compounds is discussed in terms of hydrostatic pressure effects and chemical substitution ones on them.

DOI： 10.1143/JPSJ.70.3023

Control of electronic properties of alpha-(BEDT-TTF)(2)MHg(SCN)(4) (M=K,NH4) by the uniaxial strain method 査読

M Maesato, Y Kaga, R Kondo, S Kagoshima

PHYSICAL REVIEW B 64 ( 15 ) 2001年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSICAL SOC

Systematic uniaxial strain studies of alpha-(BEDT-TTF)(2)MHg(SCN)(4) (M=K,NH4) have been carried out. By controlling the in-plane lattice parameters a and c independently, we find that both compounds have essentially the same phase diagram in electronic properties, although, under the hydrostatic pressures, they show quite different phase diagrams. The K salt shows the superconductivity like NH4 salt under the c-axis uniaxial strain, and the latter undergoes a transition to the density-wave state like the former under the a-axis uniaxial strain. These changes in electronic structures are verified by measuring the angle-dependent magnetoresistance. The electronic properties of these compounds can be systematically understood as a function of c/a, the ratio of the in-plane lattice parameters.

Neutral-ionic phase transition of (BEDT-TTF)(ClMeTCNQ) under pressure 査読

T Hasegawa, T Akutagawa, T Nakamura, T Mochida, R Kondo, S Kagoshima, Y Iwasa

PHYSICAL REVIEW B 64 ( 8 ) 2001年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSICAL SOC

Observation and characterization are reported on a neutral-ionic (NI) phase transition under pressure in (BEDT-TTF)(ClMeTCNQ), which is a mixed-stack charge-transfer compound with BEDT-TTF-based intercolumnar networks. Optical and electrical experiments revealed that the compound undergoes a pressure-induced NI transition at 1 GPa at room temperature. The temperature-pressure phase diagram of this phase transition was established by the electrical resistivity measurements at low temperature under pressure. The observed symmetry breaking in the infrared spectra and dramatic decrease of resistivity indicate that the NI transition in (BEDT-TTF)(ClMeTCNQ) at 1 GPa at room temperature is qualitatively similar in nature to that in the standard material (TTF)(CA). In contrast, the NI transition in (BEDT-TTF)(ClMeTCNQ) at low temperature under lower pressure considerably differs from that in (TTF)(CA) as to the resistivity behaviors around the phase boundary: The former becomes almost continuous without showing any anomaly, while the latter is significantly discontinuous. We discuss the origin of the observed electrical behaviors in (BEDT-TTF)(ClMeTCNQ) in terms of the effect of intercolumnar interaction associated with BEDT-TTF moieties.

Electronic properties of novel donor-acceptor type charge transfer complexes, (BETS)(2)(X(2)TCNQ) (X = Cl, Br): H-1, Se-77 and C-13-NMR 査読

K Hiraki, T Takahashi, R Kondo, S Kagoshima, T Hasegawa, T Mochida, Y Iwasa

SYNTHETIC METALS 120 ( 1-3 ) 917 - 918 2001年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA

H-1, C-13 and Se-77 NMR measurements were performed to investigate the electronic properties of (BETS)(2)(X(2)TCNQ) (X=Cl, Br). The susceptibility was decomposed into the contributions of BETS and X(2)TCNQ site. The line broadening of the H-1/Se-77 NMR spectra were observed in the Br(2)TCNQ complex at the metal insulator transition temperature, 12 K. Non magnetic spin singlet formation on the Br2TCNC2 site was observed at 80 K by C-13 NMR. Line broadening of the H-1 NMR spectra were also observed in the Cl(2)TCNQ complex at the metal insulator transition temperature. The insulating state of the Br and Cl(2)TCNQ complexes under pressure are both magnetic. The holes on the BETS layers are relevant to the magnetic ordering.

DOI： 10.1016/S0379-6779(00)01048-1

Metal-insulator transition in donor-acceptor type superconductor, (BETS)(2)(X(2)TCNQ) 査読

R Kondo, T Hasegawa, S Kagoshima, T Mochida, Y Iwasa

SYNTHETIC METALS 120 ( 1-3 ) 995 - 996 2001年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA

We found that (BETS)(2)(Cl(2)TCNQ) becomes superconducting under pressure, showing a maximum critical temperature of 1.3K at 3.5kbar. The superconductivity disappears at higher pressures and is replaced by an insulating phase. its isostructural complex with larger cell parameters, (BETS)(2)(Br(2)TCNQ), displays a metal-insulator transition at 13K under ambient pressure.

DOI： 10.1016/S0379-6779(00)00915-2

Electronic states of novel donor/acceptor type of organic superconductor, (BETS)(2)(Cl(2)TCNQ) 査読

K Hiraki, T Takahashi, R Kondo, S Kagoshima, T Hasegawa, T Mochida, Y Iwasa

JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS 62 ( 1-2 ) 401 - 403 2001年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD

H-1 and Se-77 NMR measurements have been performed to clarify the electronic properties of charge transfer complexes, (BETS)(2)(X(2)TCNQ) (X = Cl and Br). In the CI,TCNQ complex, a Korringa-like relaxation behavior has been observed in the metallic state at ambient pressure. At 6.5 kbar, where a metal-insulator (M-I) transition is induced, a sign of anitiferromagnetic ordering was observed in the insulating state at 10 K. In the Br(2)TCNQ complex, we have also found that Se-77-1/T-1 forms a peak around the M-I transition temperature and that NMR line is broadened in the insulating state. The nature of the insulating states of both compounds seem to be the same, (C) 2000 Elsevier Science Ltd. All rights reserved.

Novel electronic states of organic conductors under uniaxial stress or uniaxial strain 査読

S. Kagoshima, M. Maesato, Y. Kaga, R. Kondo

Synthetic Metals 117 ( 1-3 ) 87 - 90 2001年

Donor-acceptor-type complexes of (BEDT-TTF)(TCNQ) analogues: Peculiar magnetic transition in (BEDO-TTF)(Cl2TCNQ) 査読

T. Hasegawa, R Kondo, S. Kagoshima, Y. Iwasa, T. Mochida, T. Akutagawa, T. Nakamura

Synthetic Metals 120 991 - 992 2001年

Control of electronic properties of (formula presented) (formula presented) by the uniaxial strain method 査読

M. Maesato, Y. Kaga, R. Kondo, S. Kagoshima

Physical Review B - Condensed Matter and Materials Physics 64 ( 15 ) 2001年

記述言語：英語掲載種別：研究論文（学術雑誌）

Systematic uniaxial strain studies of (formula presented) (formula presented) have been carried out. By controlling the in-plane lattice parameters a and c independently, we find that both compounds have essentially the same phase diagram in electronic properties, although, under the hydrostatic pressures, they show quite different phase diagrams. The K salt shows the superconductivity like (formula presented) salt under the c-axis uniaxial strain, and the latter undergoes a transition to the density-wave state like the former under the a-axis uniaxial strain. These changes in electronic structures are verified by measuring the angle-dependent magnetoresistance. The electronic properties of these compounds can be systematically understood as a function of (formula presented) the ratio of the in-plane lattice parameters. © 2001 The American Physical Society.

DOI： 10.1103/PhysRevB.64.155104

Control of electronic properties of alpha-(BEDT-TTF)(2)MHg(SCN)(4) (M=K,NH4) by the uniaxial strain method 査読

Maesato M, Kaga Y, Kondo R, Kagoshima S

PHYSICAL REVIEW B 64 ( 15 ) 1551041 - 1551048 2001年

Artificial control of intermolecular distance of organic superconductors: α -type BEDT-TTF compounds 査読

S. Kagoshima, T. Shibata, H. Hirai, R. Kondo, M. Maesato

Current Applied Physics 1 ( 1 ) 72 - 76 2001年

Electronic and crystal structures of organic superconductors under the uniaxial strain 査読

S. Kagoshima, R. Kondo, M. Maesato

Current Applied Physics 1 ( 4-5 ) 307 - 311 2001年

Uniaxial strain study of organic conductors (TMTSF)₂PF₆ 査読

H. Hirai, R. Kondo, M. Maesato, T. Shibata, S. Kagoshima

Synthetic Metals 120 ( 1-3 ) 963 - 964 2001年

Uniaxial strain study of organic conductors α-(BEDT-TTF)₂MHg(SCN)₄ [M=K, NH₄] 査読

M. Maesato, Y. Kaga, R. Kondo, H. Hirai, S. Kagoshima

Synthetic Metals 120 ( 1-3 ) 941 - 942 2001年

Control of electronic properties of organic conductors by uniaxial strain method 査読

S. Kagoshima, M. Maesato, R. Kondo, T. Shibata, H. Hirai

Synthetic Metals 120 ( 1-3 ) 683 - 686 2001年

Control of electronic properties of organic conductors by hydrostatic and uniaxial compression 査読

S. Kagoshima, R. Kondo, H. Hirai, T. Shibata, Y. Kaga, M. Maesato

Physica Status Solidi (B) Basic Research 223 ( 1 ) 97 - 104 2001年

Electronic states in the spin-density wave phase of organic conductors: Roles of the coexisting 2k_F and 4k_F charge-density waves 査読

S. Kagoshima, Y. Saso, M. Maesato, R. Kondo, T. Yamaguchi, V.A. Bondarenko, T. Hasegawa

Synthetic Metals 117 ( 1-3 ) 39 - 43 2001年

Mixed-stack organic charge-transfer complexes with intercolumnar networks 査読

T Hasegawa, T Mochida, R Kondo, S Kagoshima, Y Iwasa, T Akutagawa, T Nakamura, G Saito

PHYSICAL REVIEW B 62 ( 15 ) 10059 - 10066 2000年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSICAL SOC

We report synthesis and examination of the electronic properties of an isomorphous series of mixed-stack organic charge-transfer complexes, composed of [bis(ethylenedithio) tetrathiafulvalene] (BEDT-TTF)-based electron donors and electron accepters of halogen-substituted tetracyanoquinodimethanes (TCNQ's). Single crystals of (BEDT-TTF)(Me,TCNQ), (BEDT-TTF)(CIMeTCNQ), and (BEDO-TTF)(Cl(2)TCNQ) were investigated as to their crystal structures, and optical and magnetic properties. The intermolecular overlaps between the stacked columns were comparable to the face-to-face overlap between the donor and the acceptor molecules inside the stacks. As seen from the optical and magnetic measurements, the (BEDT-TTF)(Me,TCNQ) and (BEDT-TTF)(ClMeTCNQ) complexes were neutral, while the (BEDO-TTF)(Cl(2)TCNQ), complex was found to be ionic. Among these complexes, anomalous magnetic properties were observed in the ionic complex of (BEDO-TTF)(Cl(2)TCNQ). (BEDO-TTF)(CI,TCNQ) is a magnetic insulator with Curie-Weiss behavior in magnetic susceptibility followed by a sharp drop at around 120 K, which is in sharp contrast to conventional "spin-Peierls-type'' nonmagnetic mixed-stack ionic compounds.

Uniaxial strain method for soft crystals: Application to the control of the electronic properties of organic conductors

M Maesato, Y Kaga, R Kondo, S Kagoshima

REVIEW OF SCIENTIFIC INSTRUMENTS 71 ( 1 ) 176 - 181 2000年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER INST PHYSICS

We developed the uniaxial strain method to compress a crystalline sample along any direction without involving Poisson's effect. The uniaxial strain is realized by inserting a composite of either the sample embedded in epoxy or the sample in frozen oil into a cylinder much harder than the sample composite followed by the application of external forces to a piston put on the sample composite. We verified, by using a strain gauge embedded in the epoxy or the frozen oil, that the strain thus created has the uniaxial nature. Resistance measurements on two kinds of organic conductors, alpha-(BEDT-TTF)(2)KHg(SCN)(4) and alpha-(BEDT-TTF)(2)I-3 under the uniaxial strain showed novel electric properties that have never been found under hydrostatic pressures. Their properties were found to be largely dominated by the direction of the uniaxial strain even when it is applied along directions in the conducting plane having a two-dimensional nature. (C) 2000 American Institute of Physics. [S0034-6748(00)05001-2].

DOI： 10.1063/1.1150180

Mixed-stack organic charge-transfer complexes with intercolumnar networks 査読

HASEGAWA T, MOCHIDA T, KONDO R, KAGOSHIMA S, IWASA Y, AKUTAGAWA T, NAKAMURA T, SAITO G

Physical Review B 62 ( 15 ) 10059 - 10066 2000年

Semiclassical and non-classical angular effects of magnetoresistance in (TMTSF)2X 査読

Toshihito Osada, Toshihito Osada, Nobuharu Kami, Nobuharu Kami, Ryusuke Kondo, Seiichi Kagoshima

Synthetic Metals 103 2024 - 2027 1999年6月

We have studied the semiclassical and non-semiclassical behaviors of magnetoresistance (MR) in a quasi-one-dimensional (Q1D) conductor (TMTSF)2ClO4. Based on the Boltzmann equation, we numerically investigated possible semiclassical 'angular effects', the characteristic patterns of the field-orientation-dependence of MR, in the general Q1D conductors. Particularly, we have clarified the complicated situation around B//1D-axis in which different angular effects are mixed up. The angular dependent MR features in the metallic phase of (TMTSF)2ClO4almost obey the semiclassical theory except a dip structure around B//b'. As for this non-semiclassical feature, we discuss the possibility of the one-body and many-body field-induced electron confinement onto a single conducting layer.

DOI： 10.1016/S0379-6779(98)00289-6

Organic metals involving double chain donor arrangements, (BMDT-TTF)(2)((RR2)-R-1-TCNQ) [R-1 = H, Me, R-2 = Cl, Br] 査読

T Mochida, T Hasegawa, R Kondo, S Kagoshima, Y Iwasa

SYNTHETIC METALS 102 ( 1-3 ) 1680 - 1680 1999年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA

The title compounds show unique crystal structures involving double-column donor arrangements, affording characteristic fourfold Fermi surfaces. They show metallic conductivities, accompanied by metal-insulator transitions at low temperatures.

Electronic phase transition of BEDT-TTF based mixed-stack charge-transfer complexes 査読

T Hasegawa, T Akutagawa, T Nakamura, Y Sasou, R Kondo, S Kagoshima, T Mochida, G Saito, Y Iwasa

SYNTHETIC METALS 103 ( 1-3 ) 1804 - 1805 1999年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA

The BEDT-TTF based mixed-stack charge-transfer (CT) complexes have been investigated for a series of isostructural compounds. The ionic complex of (BEDO-TTF)(Cl(2)TCNQ) is a magnetic insulator with showing Curie-Weiss behavior in magnetic susceptibility, in sharp contrast to the conventional mixed-stack CT complexes. The (BEDT-TTF)(ClMeTCNQ) compound undergoes neutral-ionic (NI) phase transition at high pressure.

Structure and properties of (BEDSe-TTF)(Fn-TCNQ) charge transfer complexes (n=1, 2, 4) 査読

T Mochida, H Moriyama, T Hasegawa, R Kondo, S Kagoshima, Y Iwasa

SYNTHETIC METALS 102 ( 1-3 ) 1678 - 1679 1999年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA

Charge transfer complexes of bis(ethylenediselena)-tetrathiafulvalene.(BEDSe-TTF) with a variety of Fn-TCNQ (n = 1, 2, 4, including isomers) are synthesized. In this family, only F-1,-TCNQ afforded a conducting complex. Other accepters gave mixed stack insulators, which undergo antiferromagnetic phase transitions. 2,5-F-2- and 2,3-F-2-TCNQ also yielded a polymorph with a novel type of crystal structure, showing a double-chain donor arrangement.

DOI： 10.1016/S0379-6779(98)00578-5

Structure and properties of ail organic conductor (BEDT-TseF)(2)(X(1)X(2)TCNQ) (X-1,X-2=Cl,Br) 査読

R Kondo, S Kagoshima, T Hasegawa, T Mochida, Y Iwasa

SYNTHETIC METALS 102 ( 1-3 ) 1628 - 1629 1999年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA

We synthesized donor-acceptor charge-transfer complexes composed of BEDT-TSeF ( or "BETS") and. TCNQ derivatives and obtained isosturctual complexes represented as (BETS)(2)(X(1)X(2)TCNQ) (X-1,X-2=Cl, Br). The single crystals of (BETS)(2)(Cl(2)TCNQ) preserve the metallic state down to 2K.

DOI： 10.1016/S0379-6779(98)00492-5

Donor-acceptor type superconductor, (BETS)(2)(Cl(2)TCNQ) 査読

R Kondo, T Hasegawa, T Mochida, S Kagoshima, Y Iwasa

CHEMISTRY LETTERS 1999 ( 4 ) 333 - 334 1999年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：CHEMICAL SOC JAPAN

It was found that (BETS)(2)(Cl(2)TCNQ) is an all-organic superconductor, where BETS is bis(ethylenedithio)tetraselenafulvalene and Cl(2)TCNQ is 2,5-dichlorotetracyanoquinodimethane. The superconducting critical temperature was 1.3 K+/-0.3 K under pressure.

DOI： 10.1246/cl.1999.333

Low-temperature diffuse X-ray studies of charge-density waves coexisting with spin-density waves in the organic conductors (TMTSF)₂PF₆ and (TMTSF)₂AsF₆ 査読

S. Kagoshima, Y. Saso, M. Maesato, R. Kondo, T. Hasegawa

Solid State Communications 110 ( 9 ) 479 - 483 1999年

Electrical properties of Zn-Mg-RE (RE=Y, Gd) icosahedral quasicrystals 査読

R Kondo, T Hashimoto, K Edagawa, S Takeuchi, T Takeuchi, U Mizutani

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 66 ( 4 ) 1097 - 1102 1997年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOC JAPAN

The electrical resistivity and the magnetoresistance have been measured for icosahedral phases of Zn-Mg-RE (RE=Y, Gd). Electrical resistivities of bulk samples of Zn56Mg36Y8, annealed ribbon samples of Zn62Mg30Y8 and annealed ribbon samples of Zn55Mg35.5Gd9.5 are 1 m Ohm cm, 0.3 m Ohm cm and 0.3 m Ohm cm. respectively. The resistivities of all the samples decrease by 5 similar to 7% from 4.2 K to 273 K. At low temperatures, the conductivity of Zn-Mg-Y obeys T-1/2 dependence, while the resistivity of Zn-Mg-Gd obeys ln T dependence, where Gd atoms bear magnetic moments. In Zn-Mg-Y; the magnetoresistance is negative and insensitive to temperature, while in Zn-h Ig-Gd it is positive in a low field range and becomes negative at high field with its magnitude larger at lower temperature. These results are interpreted by the theories of electron-electron interaction, weak localization and s-d exchange interaction.

DOI： 10.1143/JPSJ.66.1097

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