Thermodynamic behavior of the 10K class organic superconductor κ-(BEDT-TTF)2Cu(NCS)2 studied by relaxation calorimetry

Ishikawa, Tetsushi; Fujisaki, Tatsuya; Naito, Ayumi; Nakazawa, Yasuhiro; Oguni, Masaharu

doi:10.1016/j.tca.2005.01.056

Cited by 14 publications

(9 citation statements)

References 16 publications

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“…It reaches about 2.8, if the mean field peak is considered by keeping the entropy balance between the normal and the superconductive states. Shown in Figure 8 is the peak shape of the electronic heat capacity of κ-(BEDT-TTF) 2 Cu(NCS) 2 observed by Yamashita et al, which gives rather large ∆C p T −1 with 60 mJ K −2 mol −1 [25]. The data are consistent with those reported in [24].…”

Section: K Class Superconductors: κ-(Bedt-ttf) 2 Cu(ncs) 2 and κ-(supporting

confidence: 87%

“…The heat capacity measurements around T c of κ-type organic superconductors were performed mainly by thermal relaxation calorimetry and also by high-resolution ac calorimetry techniques. Up to now, several groups have reported the heat capacity measurements around T c for κ-(BEDT-TTF) 2 Cu(NCS) 2 and κ-(BEDT-TTF) 2 Cu[N(CN) 2 ]Br [24][25][26][27][28][29], but the temperature region is limited due to the difficulty of getting high-resolution data in the wide temperature range. For the former salt, the normal state electronic heat capacity coefficient γ obtained by applying magnetic fields of 12.5 T gives (25 ± 3) mJ K −2 mol −1 and a heat capacity jump ∆C p T −1 was evaluated as >50 mJ K −2 mol −1 by Andraka et al [24].…”

Section: K Class Superconductors: κ-(Bedt-ttf) 2 Cu(ncs) 2 and κ-(mentioning

confidence: 99%

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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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Section: K Class Superconductors: κ-(Bedt-ttf) 2 Cu(ncs) 2 and κ-(supporting

confidence: 87%

Section: K Class Superconductors: κ-(Bedt-ttf) 2 Cu(ncs) 2 and κ-(mentioning

confidence: 99%

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

Nakazawa

2012

Crystals

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“…The details are reported in the published literature [47][48][49][50][51]. Compared with other compounds in the figure, κ-(BEDT-TTF)2Cu(NCS)2 exhibits a rather sharp peak as shown in Figure 4c [49,50]. The thermodynamics of this compound and κ-(BEDT-TTF)2Cu[N(CN)2]Br, which has a similar transition temperature, have already been thoroughly discussed.…”

Section: Heat Capacity Of κ-(Bedt-ttf)2x Under Pressurementioning

confidence: 89%

“…Figure 4 shows the temperature dependence of the heat capacities of four charge transfer complexes, including κ-(BEDT-TTF) 2 Cu(NCS) 2 , obtained by relaxation calorimetry. The details are reported in the published literature [47][48][49][50][51]. Compared with other compounds in the figure, κ-(BEDT-TTF) 2 Cu(NCS) 2 exhibits a rather sharp peak as shown in Figure 4c [49,50].…”

Section: Heat Capacity Of κ-(Bedt-ttf) 2 X Under Pressurementioning

confidence: 93%

“…The thermodynamics of this compound and κ-(BEDT-TTF)2Cu[N(CN)2]Br, which has a similar transition temperature, have already been thoroughly discussed. Several groups have analyzed the peak shape and the magnitude of the heat capacity jump at Tc for κ-(BEDT-TTF)2Cu(NCS)2 [49,50,[52][53][54][55][56][57]. In the initial investigation stage of this material, the heat capacity jump is reported as evidence of the bulk nature of the superconductivity, as reported by Katsumoto et al [52] and Andraka et al [53].…”

Section: Heat Capacity Of κ-(Bedt-ttf)2x Under Pressurementioning

confidence: 99%

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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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Calorimetric study of molecular superconductor κ-(BEDT-TTF)2Ag(CN)2H2O which contains water in the anion layers

Ishikawa

Nakazawa

Kawamoto

et al. 2008

J Therm Anal Calorim

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Thermodynamic behavior of the 10K class organic superconductor κ-(BEDT-TTF)2Cu(NCS)2 studied by relaxation calorimetry

Cited by 14 publications

References 16 publications

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

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

Calorimetric study of molecular superconductor κ-(BEDT-TTF)2Ag(CN)2H2O which contains water in the anion layers

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