Structure and properties of a new conducting organic charge-transfer salt β-(BEDT-TTF) 2AuBr 2

Kurmoo, M.; Talham, Daniel R.; Day, Peter; Parker, I. D.; Friend, Richard H.; Stringer, Andrew M.; Howard, J.A.K.

doi:10.1016/0038-1098(87)90491-1

Cited by 60 publications

(21 citation statements)

References 20 publications

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“…The experiments were carried out on a number of crystals of k-͑BEDT-TTF͒ 2 Cu͑NCS͒ 2 , grown by conventional electrochemical means [14] and of approximate size 1 3 0.5 3 0.05 mm 3 . A single crystal was placed at the center of a silver rectangular resonant cavity of dimensions 6 3 3 3 1.5 mm 3 , resonating in the TE 102 mode at around 70 GHz; the quality factor of the cavity is ϳ1500 when empty, falling to ϳ1000 when it is loaded with the sample.…”

mentioning

confidence: 99%

Millimeter-Wave Magneto-optical Determination of the Anisotropy of the Superconducting Order Parameter in the Molecular Superconductorκ-(BEDT−TTF)2
Schrama
¹
,
Rzepniewski
²
,
Edwards
³

et al. 1999
Phys. Rev. Lett.
Self Cite
60
3
45
2
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We have used a millimeter-wave magneto-optical technique to study the angle dependence of the high-frequency conductivity of the molecular superconductor k-͑BEDT-TTF͒ 2 Cu͑NCS͒ 2 . The data strongly suggest that the superconducting gap has nodes directed along the b and c directions of the crystal, in agreement with recent theoretical predictions. This supports the idea that the superconductivity in k-͑BEDT-TTF͒ 2 Cu͑NCS͒ 2 is d wave in nature, and is mediated by spin fluctuations. PACS numbers: 74.25.Gz, 74.20.Mn, 74.25.Nf, 74.70.Kn The family of superconducting charge-transfer salts k-͑BEDT-TTF͒ 2 X, where X can, for example, be Cu͑NCS͒ 2 , Cu͓N͑CN͒ 2 ͔Br, or I 3 , has attracted considerable recent attention. A variety of experiments have suggested that the superconducting gap function may contain nodes at certain points on the Fermi surface; e.g., the 13 C NMR spin-lattice relaxation rate [1] varies as T 3 and the thermal conductivity [2] is proportional to T below the superconducting critical temperature T c . In addition, microwave penetration-depth studies [3] show a non-BCS-like behavior of the penetration depth as a function of T and the electronic component of the specific heat [4] has an unconventional field dependence below T c . However, Shubnikov-de Haas [5,6], magnetic breakdown [7], and angle-dependent magnetoresistance oscillation [8] experiments demonstrate that these salts have well-defined quasi-two-dimensional (Q2D) Fermi surfaces, indicating that the quasiparticles can be described by Fermi-liquid theory at low temperatures (the Fermi surface is shown schematically as an inset of Fig. 1). Furthermore, it has been possible to fit experimental Fermi-surface-topology data to a simplified model of the tight-binding band structure (the so-called effective dimer model) to a good degree of accuracy [5,[9][10][11].The combination of unconventional superconductivity and a tractable analytical representation of the band structure makes the k-͑BEDT-TTF͒ 2 X superconductors attractive for theoretical studies, and a number of authors [9,10,12,13] have explored the possibility of d-wave superconductivity mediated by spin fluctuations. Such approaches predict that the superconducting order parameter will have four, roughly perpendicular, gap nodes, the exact orientation of the nodes depending on the underlying details of the Fermi surface [10,12]. Experiments performed thus far have merely detected the probable presence of the gap nodes, without giving information about their relative orientation. In this paper, we use a millimeter-wave magneto-optical technique to determine the orientation of the gap nodes in k-͑BEDT-TTF͒ 2 Cu͑NCS͒ 2 . The data appear to be in good qualitative agreement with the predictions of Schmalian [10].The experiments were carried out on a number of crystals of k-͑BEDT-TTF͒ 2 Cu͑NCS͒ 2 , grown by FIG.

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mentioning

confidence: 99%

Millimeter-Wave Magneto-optical Determination of the Anisotropy of the Superconducting Order Parameter in the Molecular Superconductorκ-(BEDT−TTF)2
Schrama
¹
,
Rzepniewski
²
,
Edwards
³

et al. 1999
Phys. Rev. Lett.
Self Cite
60
3
45
2
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“…Crystallization of charge transfer salts of BEDT-TTF in the presence of AuBr2 ions produces three crystal phases (a', 5, (F) of (BEDT-TTF)2AuBr2 (Kurmoo et al 1987;Beno et al 1986;Amberger et al 1986;Mori et al 1986). The monoclinic (a') and orthorhombic (8) phases are semiconducting (Parker et al 1989;Mori et al 1986) and the triclinic ((F) phase is metallic but does not become superconducting down to 80 mK (Doporto et al 1993) and pressure up to 6 kbar (Kurmoo et al 1987). The oc' phase has a much larger cell volume per formula unit than the other two phases suggesting that the a' phase is more compressible.…”

Section: Resultsmentioning

confidence: 99%

High pressure and low temperature X-ray crystallography: the crystal structure of the molecular charge transfer salt α'- (bis(ethylenedithio)-tetrathiafulvalene) ₂ AuBr ₂

Chasseau

Gaultier

Bravic

et al. 1993

Proc. R. Soc. Lond. A

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An X-ray diffraction technique is described that allows determination of crystal structure and the variation of lattice parameters of single crystals as a function of hydrostatic pressure up to 14 kbar and of temperature from 300 K to 12 K. As an example of the technique results are presented on the molecular charge transfer salt α'-(BEDT TTF )2 AuBr 2 (BEDT-TTF = bis(ethylenedithio)-tetrathiafulvalene) to elucidate the nature of a structural phase transition which occurs at 250 K at ambient pressure and 7 kbar at 300 K. The transition, of second order, is characterized by the appearance of ½b* superlattice reflections at high pressure or low temperature but without any drastic change in the basic crystal structure. The isobaric thermal expansions and the isothermal compressibilities are anisotropic, being larger along a than along b and c , though of different magnitudes and directional properties, i. e. the effect of applying pressure at ambient temperature is not equivalent to lowering the temperature at ambient pressure. Transfer integral calculations show that marked dimerization along the stacking axis, already present at 300 K, is related to electronic localization.

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“…Based on the above results, the hump-like anomalies below 32 K in the temperature dependence of the interlayer resistance should be ascribed to a density wave transition accompanied by the variation of the electronic structure, since I) β''-CsCd has a pair of large one-dimensional Fermi surface, which may be nested and II) Actually, β"-(BEDT-TTF) 2 AuBr 2 [9,10], which has the same molecular arrangement as β''-CsCd, also has a density wave transition although they showed no remarkable anomaly in their resistance measurement [10,11,12].…”

Section: Under Magnetic Fields Parallel To the Layermentioning

confidence: 87%

Magneto-transport properties in the density wave phase of β′′-(BEDT-TTF)₂CsCd(SCN)₄

Kondo

Otsuji

Kagoshima

2006

J. Phys.: Conf. Ser.

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Structure and properties of a new conducting organic charge-transfer salt β-(BEDT-TTF) 2AuBr 2

Cited by 60 publications

References 20 publications

Millimeter-Wave Magneto-optical Determination of the Anisotropy of the Superconducting Order Parameter in the Molecular Superconductorκ-(BEDT−TTF)2
Schrama
¹
,
Rzepniewski
²
,
Edwards
³

et al. 1999
Phys. Rev. Lett.
Self Cite
60
3
45
2
View full text Add to dashboard Cite

Millimeter-Wave Magneto-optical Determination of the Anisotropy of the Superconducting Order Parameter in the Molecular Superconductorκ-(BEDT−TTF)2
Schrama
¹
,
Rzepniewski
²
,
Edwards
³

et al. 1999
Phys. Rev. Lett.
Self Cite
60
3
45
2
View full text Add to dashboard Cite

High pressure and low temperature X-ray crystallography: the crystal structure of the molecular charge transfer salt α'- (bis(ethylenedithio)-tetrathiafulvalene) ₂ AuBr ₂

Magneto-transport properties in the density wave phase of β′′-(BEDT-TTF)₂CsCd(SCN)₄

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Structure and properties of a new conducting organic charge-transfer salt β-(BEDT-TTF) 2AuBr 2

Cited by 60 publications

References 20 publications

Millimeter-Wave Magneto-optical Determination of the Anisotropy of the Superconducting Order Parameter in the Molecular Superconductorκ-(BEDT−TTF)2Schrama1, Rzepniewski2, Edwards3 et al. 1999Phys. Rev. Lett.Self Cite603452View full textAdd to dashboardCite

Millimeter-Wave Magneto-optical Determination of the Anisotropy of the Superconducting Order Parameter in the Molecular Superconductorκ-(BEDT−TTF)2Schrama1, Rzepniewski2, Edwards3 et al. 1999Phys. Rev. Lett.Self Cite603452View full textAdd to dashboardCite

High pressure and low temperature X-ray crystallography: the crystal structure of the molecular charge transfer salt α'- (bis(ethylenedithio)-tetrathiafulvalene) 2 AuBr 2

Magneto-transport properties in the density wave phase of β′′-(BEDT-TTF)2CsCd(SCN)4

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Millimeter-Wave Magneto-optical Determination of the Anisotropy of the Superconducting Order Parameter in the Molecular Superconductorκ-(BEDT−TTF)2
Schrama
¹
,
Rzepniewski
²
,
Edwards
³

et al. 1999
Phys. Rev. Lett.
Self Cite
60
3
45
2
View full text Add to dashboard Cite

Millimeter-Wave Magneto-optical Determination of the Anisotropy of the Superconducting Order Parameter in the Molecular Superconductorκ-(BEDT−TTF)2
Schrama
¹
,
Rzepniewski
²
,
Edwards
³

et al. 1999
Phys. Rev. Lett.
Self Cite
60
3
45
2
View full text Add to dashboard Cite

High pressure and low temperature X-ray crystallography: the crystal structure of the molecular charge transfer salt α'- (bis(ethylenedithio)-tetrathiafulvalene) ₂ AuBr ₂

Magneto-transport properties in the density wave phase of β′′-(BEDT-TTF)₂CsCd(SCN)₄