Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Applied Physics  

DOI： 10.7566/jpsj.89.074706

researchmap

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：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

Web of Science

researchmap

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：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

Web of Science

researchmap

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

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

Web of Science

Scopus

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：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

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：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

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：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

Web of Science

researchmap

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

We studied the low-temperature electrical properties of the two-dimensional organic conductor beta ''-(BEDT-TTF)(2)AuBr2, whose electronic structure is similar to that of the pressure-induced superconductor beta ''-(DODHT)(2)PF6 having a charge-ordered transition at 255 K at ambient pressure. We found that the ground state of beta ''-(BEDT-TTF)(2)AuBr2 at ambient pressure has a charge-density-wave phase below 6.5 K accompanied by x-ray superlattice spots. We also discovered superconductivity in the vicinity of the charge-density-wave phase by applying uniaxial strain. Based on the obtained results, we propose a unified electronic phase diagram that suggests the relationships among the charge-ordered insulating state, the superconducting phase, and the charge-density-wave phase in beta ''-type organic conductors. The phase diagram shows that the superconducting phase is located near the charge-density-wave phase, which suggests that spin fluctuations play a minor role in the mechanism of the superconductivity and sheds light on the possibility of charge-fluctuation-mediated superconductivity in this type of organic conductor.

DOI： 10.1103/PhysRevB.81.024519

Web of Science

CiNii Article

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：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

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：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

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：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

Web of Science

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：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

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：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

Web of Science

researchmap

Publishing type：Research paper (scientific journal)   Publisher：IOP Publishing  

DOI： 10.1088/1742-6596/132/1/012023

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：PHYSICAL SOC JAPAN  

We investigate the low-temperature electronic phase of a two-dimensional organic conductor, (BEDT-TTF)(2)CsCd(SCN)(4) [where BEDT-TTF denotes bis(ethylenedithio)tetrathiafulvalene], which has a large hump between 32 and around 5 K in the temperature dependence of the interlayer resistance. We present experimental results for the temperature dependence of the resistance under magnetic fields and its Kohler plots, and an x-ray diffraction study. We find that I) Kohler's rule is strongly violated below 32 K, although the rule is valid above 32 K, and II) weak superlattice spots appear at 15.6 K in the x-ray study. On the basis of the experimental results, we suggest that the origin of the resistance hump is the formation of a possible charge density wave transition at about 32 K by the nesting of a pair of large one-dimensional Fermi surfaces obtained in the electronic structure calculation based on the crystal structure at room temperature.

DOI： 10.1143/JPSJ.77.063702

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：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

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：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

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：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

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：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

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：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

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：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

Web of Science

researchmap

Language：English   Publisher：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

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

DOI： 10.1021/ja060979+

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：PHYSICAL SOC JAPAN  

In order to investigate the relationships between crystal structures and electronic properties of theta-type BEDT-TTF organic conductors, electrical properties of theta-(BEDT-TTF)(2)Ag(CN)(2) and theta-(BEDT-TTF)(2)CsZn(SCN)(4) and crystal structures of theta-(BEDT-TTF)(2)CsZn(SCN)(4) tinder uniaxial strain are investigated. The resistivity measurements for both salts tinder uniaxial strain show that the intercolumnar uniaxial strain preserves the metallic nature while the infra-columnar one induces an insulating behavior, which are reminiscent of the charge-ordered state of theta-(BEDT-TTF)(2)RbZn(SCN)(4). Structure analyses of theta-(BEDT-TTF)(2)CsZn(SCN)(4) under uniaxial strain indicate that the inter-columnar strain slightly increases the diagonal transfer integral but does not vary the vertical one. and the infra-columnar uniaxial strain largely increases the vertical transfer integral but does not change the diagonal one. Based on these experimental results, the key parameters to determine the electrical properties of theta-type BEDT-TTF salts are discussed. It is suggested that the transfer integral along the infra-columnar direction dominates the occurence of the charge-ordered state.

DOI： 10.1143/JPSJ.75.044716

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：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).

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：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

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：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

Web of Science

Scopus

researchmap

Other Link： http://orcid.org/0000-0003-1022-430X

Language：English   Publishing type：Research paper (scientific journal)   Publisher：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

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：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

Web of Science

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：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

Web of Science

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：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

Web of Science

Scopus

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：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

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

Transport measurements of a pressure-induced organic superconductor, beta(")-(DODHT)(2)PF6 [DODHT=(1,4-dioxane-2,3-diyldithio)dihydrotetrathiafulvalene], were performed under various pressures to obtain a pressure-temperature phase diagram. The pressure application of 13.2 kbar induced superconductivity at 2.3 K. Due to a fractional existence of superconductivity, a resistive state was observed with decreasing temperature in a narrow pressure range above 13.2 kbar. X-ray and magnetic measurements at ambient pressure revealed that the insulating state has a charge disproportionation, or a charge ordering (CO) state, with stripes along the molecular side-by-side direction. These results suggest that the charge fluctuation may play a crucial role in the superconductivity in beta(")-(DODHT)(2)PF6.

DOI： 10.1103/PhysRevB.72.052510

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：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

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：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

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：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

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：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

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

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.

Scopus

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：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

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

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.

Scopus

researchmap

Language：English  

DOI： 10.1016/S0379-6779(02)00336-3

researchmap

Language：English  

DOI： 10.1016/S0379-6779(02)01037-8

J-GLOBAL

researchmap

Language：English  

DOI： 10.1016/S0921-4534(02)02760-0

researchmap

Language：English  

DOI： 10.1016/S0379-6779(02)00338-7

J-GLOBAL

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

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

Scopus

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：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

Web of Science

researchmap

Language：English  

DOI： 10.1080/10587250210805

researchmap

Language：English  

DOI： 10.1080/10587250290101397

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：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

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：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.

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：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

Web of Science

CiNii Article

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：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

Web of Science

CiNii Article

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：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.

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

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

Scopus

researchmap

Language：English   Publisher：AMERICAN PHYSICAL SOC  

DOI： 10.1103/PhysRevB.64.155104

CiNii Article

researchmap

Language：English  

DOI： 10.1016/S1567-1739(00)00014-6

researchmap

Language：English  

DOI： 10.1016/S1567-1739(01)00029-3

researchmap

Language：English  

DOI： 10.1016/S0379-6779(00)00691-3

researchmap

Language：English  

DOI： 10.1016/S0379-6779(00)01178-4

researchmap

Language：English  

DOI： 10.1016/S0379-6779(00)01104-8

J-GLOBAL

researchmap

Language：English  

DOI： 10.1002/1521-3951(200101)223:1<97::AID-PSSB97>3.0.CO;2-M

J-GLOBAL

researchmap

Language：English  

DOI： 10.1016/S0379-6779(00)00536-1

researchmap

Language：English  

DOI： 10.1016/S0379-6779(00)00543-9

researchmap

Language：English  

DOI： 10.1016/S0379-6779(00)00897-3

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：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.

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：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

Web of Science

researchmap

DOI： 10.1103/PhysRevB.62.10059

CiNii Article

researchmap

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 &#039;angular effects&#039;, 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&#039;. 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

Scopus

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：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.

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：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.

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：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

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：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

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：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

Web of Science

researchmap

Language：English  

DOI： 10.1016/S0038-1098(99)00113-1

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：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

Web of Science

CiNii Article

researchmap

Event date： 2016.9.13 - 2016.9.16

researchmap

Event date： 2015.3.21 - 2015.3.24

researchmap

Event date： 2014.8.22

Language：Japanese  

researchmap

Event date： 2014.3.5

Language：Japanese  

researchmap

Event date： 2014

researchmap

Event date： 2013.3.26

Language：Japanese  

researchmap

Event date： 2013.3.26

Language：Japanese  

researchmap

Event date： 2013

researchmap

Event date： 2012.8.24

Language：Japanese  

researchmap

Event date： 2012.3.5

Language：Japanese  

researchmap

Event date： 2012.3.5

Language：Japanese  

researchmap

Event date： 2012.3.5

Language：Japanese  

researchmap

Event date： 2012.3.5

Language：Japanese  

researchmap

Event date： 2012

researchmap

Event date： 2012

researchmap

Event date： 2012

researchmap

Event date： 2011.8.24

Language：Japanese  

researchmap

Event date： 2011.5

Language：Japanese  

researchmap

Event date： 2011.3.3

Language：Japanese  

researchmap

Event date： 2011.3.3

Language：Japanese  

researchmap

Event date： 2011.3.3

Language：Japanese  

researchmap

Event date： 2011.3.3

Language：Japanese  

researchmap

Event date： 2011.3.3

Language：Japanese  

researchmap

Event date： 2011

researchmap

Event date： 2010.7

researchmap

Event date： 2010.3.1

Language：Japanese  

researchmap

Event date： 2010.3.1

Language：Japanese  

researchmap

Event date： 2010.3.1

Language：Japanese  

researchmap

Event date： 2010

Language：Japanese  

researchmap

Event date： 2009.8.18

Language：Japanese  

researchmap

Event date： 2009.8.18

Language：Japanese  

researchmap

Event date： 2009.8.18

Language：Japanese  

researchmap

Event date： 2009.8.18

Language：Japanese  

researchmap

Event date： 2009.3.3

Language：Japanese  

researchmap

Event date： 2009.3.3

Language：Japanese  

researchmap

Event date： 2009.3.3

Language：Japanese  

researchmap

Event date： 2009

researchmap

Event date： 2008.8.25

Language：Japanese  

researchmap

Event date： 2008.8.25

Language：Japanese  

researchmap

Event date： 2008.8.25

Language：Japanese  

researchmap

Event date： 2008.2.29

Language：Japanese  

researchmap

Event date： 2008.2.29

Language：Japanese  

researchmap

Event date： 2008.2.29

Language：Japanese  

researchmap

Event date： 2008

Language：Japanese  

researchmap

Other Link： http://hdl.handle.net/2433/142598

Event date： 2008

researchmap

Event date： 2007.8.21

Language：Japanese  

researchmap

Event date： 2007.8.21

Language：Japanese  

researchmap

Event date： 2007.8.21

Language：Japanese  

researchmap

Event date： 2007.2.28

Language：Japanese  

researchmap

Event date： 2007.2.28

Language：Japanese  

researchmap

Event date： 2007.2.28

Language：Japanese  

researchmap

Event date： 2007

researchmap

Event date： 2006.8.18

Language：Japanese  

researchmap

Event date： 2006.8.18

Language：Japanese  

researchmap

Event date： 2006.8.18

Language：Japanese  

researchmap

Event date： 2006.8.18

Language：Japanese  

researchmap

Event date： 2006.8.18

Language：Japanese  

researchmap

Event date： 2006.8.18

Language：Japanese  

researchmap

Event date： 2006.3.4

Language：Japanese  

researchmap

Event date： 2006.3.4

Language：Japanese  

researchmap

Event date： 2006.3.4

Language：Japanese  

researchmap

Event date： 2006.3.4

Language：Japanese  

researchmap

Event date： 2005.8.19

Language：Japanese  

researchmap

Event date： 2005.8.19

Language：Japanese  

researchmap

Event date： 2005.3.4

Language：Japanese  

researchmap

Event date： 2005.3.4

Language：Japanese  

researchmap

Event date： 2005.3.4

Language：Japanese  

researchmap

Event date： 2005.3.4

Language：Japanese  

researchmap

Event date： 2004.11

Language：English  

researchmap

Event date： 2004.8.25

Language：Japanese  

researchmap

Event date： 2004.8.25

Language：Japanese  

researchmap

Event date： 2004.8.25

Language：Japanese  

researchmap

Event date： 2004.3.11

Language：Japanese  

researchmap

Event date： 2004.3.3

Language：Japanese  

researchmap

Event date： 2004.3.3

Language：Japanese  

researchmap

Event date： 2004.3.3

Language：Japanese  

researchmap

Event date： 2003.3.6

Language：Japanese  

researchmap

Event date： 2003.3.6

Language：Japanese  

researchmap

Event date： 2003

Language：English  

For the organic conductor $\theta$-(TMET-TTP)4PF6 (TMET-TTP: 2-[4,5-bis(methylthio)-1,3-dithiol-2-ylidene]-5-(4,5-ethylenedithio-1,3-dithiol-2-ylidene)-1,3,4,6-tetrathiapentalene), electrical resistance has been measured under the uniaxial strain applied along the $a$-, $b$-, and $c$-axes as well as under hydrostatic pressure. Contrary to the prediction of the universal phase diagram in which the $c$-axis strain will raise the metal–insulator transition temperature by expanding the dihedral angle, the insulating state is suppressed under the strain in all directions. The results are interpreted in terms of the increasing intra-stack transfer integral in the large dihedral angle region.

researchmap

Other Link： https://jlc.jst.go.jp/DN/JALC/00208627900?from=CiNii

Event date： 2002.7

Language：English  

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.

researchmap

Event date： 2002.3.1

Language：Japanese  

researchmap

Event date： 2002.3.1

Language：Japanese  

researchmap

Event date： 2002

researchmap

Event date： 2001.9.3

Language：Japanese  

researchmap

Event date： 2001.9.3

Language：Japanese  

researchmap

Event date： 2001.8.15

Language：English  

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.

researchmap

Event date： 2001.3.9

Language：Japanese  

researchmap

Event date： 2001.3.9

Language：Japanese  

researchmap

Event date： 2001.3.9

Language：Japanese  

researchmap

Event date： 2001.3.9

Language：Japanese  

researchmap

Event date： 2001.3.9

Language：Japanese  

researchmap

Event date： 2001.3.9

Language：Japanese  

researchmap

Event date： 2001.3

Language：English  

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.

researchmap

Event date： 2001.3

Language：English  

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.

researchmap

Event date： 2000.9.10

Language：Japanese  

researchmap

Event date： 2000.9.10

Language：Japanese  

researchmap

Event date： 2000.9.10

Language：Japanese  

researchmap

Event date： 2000.5

Language：Japanese  

researchmap

Event date： 2000.3.10

Language：Japanese  

researchmap

Event date： 2000.3.10

Language：Japanese  

researchmap

Event date： 2000.3.10

Language：Japanese  

researchmap

Event date： 2000

researchmap

Event date： 1999.12.5

Language：Japanese  

researchmap

Event date： 1999.9.3

Language：Japanese  

researchmap

Event date： 1999.9.3

Language：Japanese  

researchmap

Event date： 1999.9.3

Language：Japanese  

researchmap

Event date： 1999.9.3

Language：Japanese  

researchmap

Event date： 1999.6

Language：English  

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.

researchmap

Event date： 1999.6

Language：English  

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.

researchmap

Event date： 1999.3.15

Language：Japanese  

researchmap

Event date： 1999.3.15

Language：Japanese  

researchmap

Event date： 1999.3.15

Language：Japanese  

researchmap

Event date： 1999.3.15

Language：Japanese  

researchmap

Event date： 1999.3.15

Language：Japanese  

researchmap

Event date： 1998.9.5

Language：Japanese  

researchmap

Event date： 1998.9.5

Language：Japanese  

researchmap

Event date： 1998.3.10

Language：Japanese  

researchmap

Event date： 1998.3.10

Language：Japanese  

researchmap

Event date： 1995.9.12

Language：Japanese  

researchmap

Event date： 1995.9.12

Language：Japanese  

researchmap

Event date： 1995.9.12

Language：Japanese  

researchmap

Event date： 1995.3.16

Language：Japanese  

researchmap