A NEW MOLECULAR SUPERCONDUCTOR, (BEDT-TTF)2(I3)1−x(AuI2)x(x&amp;lt;0.02)

Kobayashi, Hayao; Kato, Reìzo; Kobayashi, Akiko; Nishio, Y.; Kajita, Kôji; Sasaki, Wataru

doi:10.1246/cl.1986.789

Cited by 105 publications

(66 citation statements)

References 11 publications

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“…Accordingly, the temperature range of the highly conductive phase expands to the low-temperature region, as φ is decreased. In the small φ region, X = I 3 (φ = 100°) [80] and X=CsZn(SCN) 4 (φ = 104°) [81] salts, the high-temperature phase is metallic, with dρ/dT > 0, whereas it is non-metallic, with dρ/dT < 0 above the CO transition temperature in the large φ region. The activation energy increases with increasing φ as follows: 0.02 eV for X = RbZn(SCN) 4 (φ = 111°) [81], 0.08 eV for orthorhombic TlZn(SCN) 4 (φ = 117°) [81], 0.11 eV for monoclinic TlZn(SCN) 4 (φ = 121°) [81], and 0.17-0.19 eV for Cu 2 (CN)[N(CN) 2 ] 2 (φ = 132°) [82].…”

Section: θ-(Bedt-ttf) 2 Xmentioning

confidence: 99%

Infrared and Raman Studies of Charge Ordering in Organic Conductors, BEDT-TTF Salts with Quarter-Filled Bands

Yakushi

2012

Crystals

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This paper reviews charge ordering in the organic conductors, β″-(BEDT-TTF) (TCNQ), θ-(BEDT-TTF) 2 X, and α-(BEDT-TTF) 2 X. Here, BEDT-TTF and TCNQ represent bis(ethylenedithio)tetrathiafulvalene and 7,7,8,8-tetracyanoquinodimethane, respectively. These compounds, all of which have a quarter-filled band, were evaluated using infrared and Raman spectroscopy in addition to optical conductivity measurements. It was found that β″-(BEDT-TTF)(TCNQ) changes continuously from a uniform metal to a chargeordered metal with increasing temperature. Although charge disproportionation was clearly observed, long-range charge order is not realized. Among six θ-type salts, four compounds with a narrow band show the metal-insulator transition. However, they maintain a large amplitude of charge order (Δρ~0.6) in both metallic and insulating phases. In the X = CsZn(SCN) 4 salt with intermediate bandwidth, the amplitude of charge order is very small (Δρ < 0.07) over the whole temperature range. However, fluctuation of charge order is indicated in the Raman spectrum and optical conductivity. No indication of the fluctuation of charge order is found in the wide band X = I 3 salt. In α-(BEDT-TTF) 2 I 3 the amplitude of charge order changes discontinuously from small amplitude at high temperature to large amplitude (Δρ max~0 .6) at low temperature. The long-range chargeordered state shows ferroelectric polarization with fast optical response. The fluctuation of multiple stripes occurs in the high-temperature metallic phase. Among α-(BEDT-TTF) 2 MHg(SCN) 4 (X = NH 4 , K, Rb, Tl), the fluctuation of charge order is indicated only in the X = NH 4 salt. α′-(BEDT-TTF) 2 IBr 2 shows successive phase transitions to the ferroelectric state keeping a large amplitude of charge order (Δρ max~0 .8) over the whole temperature range. It was found that the amplitude and fluctuation of charge order in these compounds is enhanced as the kinetic energy (bandwidth) decreases. OPEN ACCESSCrystals 2012, 2 1292

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Section: θ-(Bedt-ttf) 2 Xmentioning

confidence: 99%

Infrared and Raman Studies of Charge Ordering in Organic Conductors, BEDT-TTF Salts with Quarter-Filled Bands

Yakushi

2012

Crystals

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“…Coexistence of foreign chemical species (dopants) in synthesis sometimes led to unexpected change in crystal structures and thus in physical properties [13,14]. It is very difficult to control exact amount of dopant and the precise part to be doped by chemical mixing methods.…”

Section: Introductionmentioning

confidence: 99%

Photochemical modification of magnetic properties in organic low-dimensional conductors

Naito

Kakizaki

Wakeshima

et al. 2009

Journal of Solid State Chemistry

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Magnetic properties of organic charge transfer salts Ag(DX) 2 (DX = 2,5-dihalogeno-N,N'-dicyanoquinonediimine; X = Cl, Br, I) were modified by UV irradiation from paramagnetism to diamagnetism in an irreversible way. The temperature dependence of susceptibility revealed that such change in magnetic behavior could be continuously controlled by the duration of irradiation. The observation with scanning electron microprobe revealed that the original appearance of samples, e.g. black well-defined needle-shaped shiny single crystals, remained after irradiation irrespective of the irradiation conditions and the duration. Thermochemical analysis and X-ray diffraction study demonstrated that the change in the physical properties were due to (partial) decomposition of Ag(DX) 2 to AgX, which was incorporated in the original Ag(DX) 2 lattices. Because the physical properties of  Corresponding author: tnaito@sci.hokudai.ac.jp 2 low-dimensional organic conductors are very sensitive to lattice defects, even a small amount of AgX could effectively modify the electronic properties of Ag(DX) 2 without making the original crystalline appearance collapse.

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“…In some BEDT-TTF salts, superconductivity appears directly after the suppression of the CO transition by applying chemical or mechanical pressure [10][11][12]. However, the CO transition temperature is much higher than the SC transition temperature T c [13,14], and the two phenomena thus appear * yihara@phys.sci.hokudai.ac.jp unrelated. In the BEDT-TTF salt with β -type molecular packing, β -(BEDT-TTF) 4 [(H 3 O)Ga(C 2 O 4 ) 3 ]·C 6 H 5 NO 2 (β -Ga), a charge instability was observed below 8.5 K, very close to the SC transition temperature T c = 7 K [15,16].…”

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confidence: 99%

“…As in the case of other BEDT-TTF salts, this high-temperature CO may not be directly related to the SC pairing mechanism, because the temperature scale for a charge transition is one order of magnitude larger than that for superconductivity. Subsequent 13 C NMR spectroscopy detected another charge anomaly below 12 K [15]. This charge anomaly near T c should be examined to understand the electronic state at low temperatures where superconductivity sets in.…”

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C13NMR study of the charge-ordered state near the superconducting transition in the organic superconductorβ′′−(BEDT-T

et al. 2014

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The charge-ordered state in a quasi-two-dimensional organic superconductor β -(BEDT-TTF) 4 [(H 3 O)Ga(C 2 O 4 ) 3 ]·C 6 H 5 NO 2 has been investigated using 13 C NMR spectroscopy in a high magnetic field. Enhanced resolution of the high-field spectrum allows us to estimate the site charges in the low-temperature charge-ordered state below 8.5 K. The observed strong increase in the charge imbalance suggests that superconductivity appears on the electronic state with a strong charge modulation. From the NMR intensity ratio of signals from the charge-rich and charge-poor sites, we discuss a possible charge pattern with threefold modulation, which could be stabilized by the effects of electron-electron correlations. Unconventional superconductivity is frequently observed near the boundary of other ordered phases. In high-T c pnictides and heavy fermion superconductors, superconductivity appears next to an antiferromagnetic phase, and its mechanism is related to the critical fluctuations of the second-order phase transition. By analogy with antiferromagnetism near superconductivity, the charge-ordering (CO) transition near the superconducting (SC) phase would also be related to the SC pairing mechanisms. In fact, it has been suggested theoretically that the charge fluctuations can contribute to form Cooper pairs both in the context of cuprates [1] and layered molecular crystals [2]. As in most of materials the SC and CO transitions appear at very different temperatures, particular attention should be paid to rare examples where these transitions (and related energy scales) are close [3], to reveal experimentally the complex relationship, perhaps not only competition, between the CO and SC phases.Electronic charge localization is caused by a strong electron-electron interaction in half-filled or quarter-filled systems. The effects of on-site and off-site Coulomb interactions have been intensively investigated both from theoretical and experimental points of view [4][5][6]. In low-dimensional electronic systems, such as NbSe 3 [7] and organic conductor (TMTTF) 2 X (tetramethyltetrathiafulvalene) salts [8], the charge-density-wave (CDW) state with fractional charge localization is driven by Fermi surface instability. Although these systems show superconductivity under pressure, the CDW state of NbSe 3 is completely suppressed when superconductivity sets in [9], and in (TMTTF) 2 X a magnetic phase appears between the SC and CDW phases. Charge instability is also observed in quasi-two-dimensional organic conductors (BEDT-TTF) 2 X [bis(ethylenedithio)-tetrathiafulvalene] salts. In some BEDT-TTF salts, superconductivity appears directly after the suppression of the CO transition by applying chemical or mechanical pressure [10][11][12]. However, the CO transition temperature is much higher than the SC transition temperature T c [13,14], and the two phenomena thus appear * yihara@phys.sci.hokudai.ac.jp unrelated. In the BEDT-TTF salt with β -type molecular packing, β -(BEDT-TTF) 4 [(H 3 O)Ga(C 2 O 4 ) 3 ]·C 6 H 5 NO 2 (β -Ga)...

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A NEW MOLECULAR SUPERCONDUCTOR, (BEDT-TTF)2(I3)1−x(AuI2)x(x<0.02)

Cited by 105 publications

References 11 publications

Infrared and Raman Studies of Charge Ordering in Organic Conductors, BEDT-TTF Salts with Quarter-Filled Bands

Infrared and Raman Studies of Charge Ordering in Organic Conductors, BEDT-TTF Salts with Quarter-Filled Bands

Photochemical modification of magnetic properties in organic low-dimensional conductors

C13NMR study of the charge-ordered state near the superconducting transition in the organic superconductorβ′′−(BEDT-T

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