Low-temperature heat capacity measurements of κ-type organic superconductors under pressure

Nozomi, Tokoro; Fukuoka, Shin-Ichi; Kubota, Osamu; Nakazawa, Yasuhiro

doi:10.1016/j.physb.2009.12.087

Cited by 5 publications

(4 citation statements)

References 18 publications

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“…Figure 6a shows the temperature dependence of the ac heat capacity at 0.15 GPa and Figure 6b shows the result of the similar analysis as was performed for ambient pressure data in Figure 5b. The transition temperature is reduced to about 5-6 K, which is consistent with the results of the proceeding work [44]. Subtracting the 7-T data also gives the relative change of the electronic heat capacity contribution ∆C p for each field, which is shown in the ∆C p T −1 vs. T plot in Figure 6b.…”

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

confidence: 87%

“…However, the latter may have some extra effects related to the frustration due to the increase in the triangularity in the molecular arrangement of the dimer units. We have also reported the suppression of the peak by pressure in κ-(BEDT-TTF)2Ag(CN)2H2O [44]. These features are consistent with κ-(BEDT-TTF)2Cu(NCS)2, as summarized in Figure 7.…”

Section: κ-(Bedt-ttf)2cu[n(cn)2]br and κ-[(Bedt-ttf)1−x(bedse-ttf)x]2supporting

confidence: 85%

“…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%

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

confidence: 87%

Section: κ-(Bedt-ttf)2cu[n(cn)2]br and κ-[(Bedt-ttf)1−x(bedse-ttf)x]2supporting

confidence: 85%

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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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show abstract

“…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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Thermal anomaly around the superconductive transition of κ-(BEDT-TTF)2Cu(NCS)2 with external pressure and magnetic field control

Muraoka

Imajo

Akutsu

et al. 2016

J Therm Anal Calorim

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Low-temperature heat capacity measurements of κ-type organic superconductors under pressure

Cited by 5 publications

References 18 publications

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

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

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

Thermal anomaly around the superconductive transition of κ-(BEDT-TTF)2Cu(NCS)2 with external pressure and magnetic field control

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