Thermodynamic study of κ-(BEDT-TTF)2Ag(CN)2H2O under pressures and with magnetic fields

Nozomi, Tokoro; Kubota, Osamu; Kawamoto, Atsushi; Nakazawa, Yasuhiro

doi:10.1088/1742-6596/132/1/012010

Cited by 7 publications

(3 citation statements)

References 18 publications

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“…To see the variation of superconductive characters in the phase diagram of κ-type salts, a.c. heat capacity measurements under controlled pressure are performed by Tokoro et al. , in κ-(BEDT-TTF) 2 Ag(CN) 2 H 2 O, κ-(BEDT-TTF) 2 Cu(NCS) 2 , and κ-(BEDT-TTF 1– x BEDSe-TTF x ) 2 Cu[N(CN) 2 ]Br system. The substitution of BEDT-TTF by BEDSe-TTF molecules less than 20% produces a chemical pressure effect and decreases the transition temperature.…”

Section: Organic Conductorsmentioning

confidence: 99%

Update 1 of: Calorimetric Investigation of Phase Transitions Occurring in Molecule-Based Magnets

et al. 2013

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Section: Organic Conductorsmentioning

confidence: 99%

Update 1 of: Calorimetric Investigation of Phase Transitions Occurring in Molecule-Based Magnets

et al. 2013

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“…The comparison of thermodynamic behaviors produced by chemical pressure effects with those obtained under hydrostatic pressures are required. In order to get thermodynamic data under pressure, the ac calorimetric system for single crystal samples of organic salts were developed by Kubota et al [50] and Tokoro et al [50,51]. Two small ruthenium oxide sensor chips with 100 Ω and 1 kΩ were used as a thermometer and a heater respectively, and small temperature modulation was detected by a four probe technique with a high resolution ac bridge system.…”

Section: Heat Capacities Under Pressures For κ-(Bedt-ttf) 2 X Supercomentioning

confidence: 99%

Thermodynamic Properties of κ-(BEDT-TTF)2X Salts: Electron Correlations and Superconductivity

Nakazawa

2012

Crystals

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Abstract:Heat capacity measurements of κ-(BEDT-TTF) 2 X (BEDT-TTF: Bis(ethylendithio) tetrathiafulvalene, X: counteranions) which are classified as two-dimensional (2D) dimer-Mott system are reported. At first, we explain structural and electronic features originated from rigid dimerization in donor arrangement in 2D layers. The antiferromagnetic Mott insulating phase located at low-pressure region in the phase diagram shows vanishing γ electronic heat capacity coefficient in the heat capacity, which claims opening of a charge-gap in this insulating state. Then, a systematic change of the γ around the Mott boundary region is reported in relation to the glass freezing of ethylene dynamics. The thermodynamic parameters determined by ∆C p /γT c of 10 K class superconductors, κ-(BEDT-TTF) 2 Cu(NCS) 2 and κ-(BEDT-TTF) 2 Cu[N(CN) 2 ]Br demonstrate that a rather large gap with a strong coupling character appears around the Fermi-surface. On the other hand, the low temperature heat capacity clearly shows a picture of nodal-gap structure due to an anisotropic pairing. The comparison with lower T c compounds in the κ-type structure is also performed so as to discuss overall features of the κ-type superconductors. The heat capacity measurements of hole-doped systems containing mercury in the counteranions show an anomalous enhancement of γ, which is consistent with the T 1 −1 of NMR experiments etc. The results of heat capacity measurements under high pressures are also reported. OPEN ACCESSCrystals 2012, 2 742

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“…Measurements are available over a wide temperature range from a low temperature of about 0.7 K up to about 20 K while reducing the sample amount to 200 µg-2 mg [41][42][43][44][45]. The construction details are reported elsewhere [33,41,42].…”

Section: Calorimetry Apparatus To Measure the Heat Capacity Under Prementioning

confidence: 99%

Thermodynamic Picture of Dimer-Mott Organic Superconductors Revealed by Heat Capacity Measurements with External and Chemical Pressure Control

et al. 2018

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This article reviews and discusses the thermodynamic properties of dimer-Mott-type molecular superconductive compounds with (BEDT-TTF) 2 X composition, where BEDT-TTF is bis(ethylenedithio)tetrathiafulvalene and X denotes counter-anions, respectively. We focus mainly on the features occurring in the κ-type structure in which the d-wave superconductive phase appears depending on the Coulomb repulsion U and the bandwidth W, which is tunable by external and chemical pressures. First, we report the high-pressure ac (alternating current) calorimetry technique and experimental system constructed to measure single-crystal samples of molecule-based compounds to derive low-temperature thermodynamic parameters. Using extremely small resistance chips as a heater and a thermometer allows four-terminal detection of an accurate temperature and its oscillation in the sample part with sufficient sensitivity. From the analyses of the temperature dependence of the ac heat capacity of κ-(BEDT-TTF) 2 Cu(NCS) 2 under external pressures, we discuss the changes in the peak shape of the thermal anomaly at the superconductive transition temperature T c at various external pressures p. The rather sharp peak in C p T −1 at T c = 9.1 K with a strong coupling character at ambient pressure is gradually reduced to weaker coupling as the pressure increases to 0.45 GPa concomitant with suppression of the transition temperature. This feature is compared with the systematic argument of the chemical-pressure effect on the basis of thermal anomalies around the superconductive transition of κ-(BEDT-TTF) 2 X compounds and other previously studied typical dimer-Mott 2:1 compounds. Finally, the discussion is extended to the chemical pressure effect on the normal state electronic heat capacity coefficient γ obtained by applying magnetic fields higher than H c2 and the residual γ*, which remains in the superconductive state due to the induced electron density of states around the node structure. From the overall arguments with respect to both chemical and external pressures, we suggest that a crossover of the electronic state inside the superconductive phase occurs and the coupling strength of electron pairs varies from the electron correlation region near the metal-insulator boundary to the band picture region.

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Thermodynamic study of κ-(BEDT-TTF)₂Ag(CN)₂H₂O under pressures and with magnetic fields

Cited by 7 publications

References 18 publications

Update 1 of: Calorimetric Investigation of Phase Transitions Occurring in Molecule-Based Magnets

Update 1 of: Calorimetric Investigation of Phase Transitions Occurring in Molecule-Based Magnets

Thermodynamic Properties of κ-(BEDT-TTF)2X Salts: Electron Correlations and Superconductivity

Thermodynamic Picture of Dimer-Mott Organic Superconductors Revealed by Heat Capacity Measurements with External and Chemical Pressure Control

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