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Sample records for bedt-ttf

  1. Magnetooptical measurements of {beta}''-(BEDT-TTF)(TCNQ)

    Energy Technology Data Exchange (ETDEWEB)

    Kimata, M.; Oshima, Y.; Ohta, H.; Koyama, K.; Motokawa, M.; Yamamoto, H.M.; Kato, R

    2004-04-30

    Magnetooptical measurements have been performed on {beta}''-(BEDT-TTF)(TCNQ) using the cavity perturbation techniques. {beta}''-(BEDT-TTF)(TCNQ) has very exotic Fermi surface (FS). Several harmonic resonances were observed at various angles. We consider these resonances as q1D-periodic orbit resonance. The obtained Fermi velocity and the scattering time are 4.4x10{sup 4} m/s and 2.1x10{sup -11} s, respectively. When the magnetic field was rotated in the b{sup *}a-plane, the similar resonances are observed. According to these results, the FS topology of the system at low temperature is discussed.

  2. Synthesis and Electrochemical Studies on BEDT-TTF Derivatives with Hydroxyl Groups

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    New electron donors with hydroxyl groups were synthesized and characterized spectroscopically.Their redox potentials were determined with cyclic voltammetry, and the comparison with BEDT-TTF [Bis(ethylenedithio)tetrathiafulvalene] in this aspect was made.These results indicated that the new electron donors had similar electron-donating capabilities as BEDT-TTF.

  3. Chiral conductors from BEDT-TTF and related chiral donor molecules

    Energy Technology Data Exchange (ETDEWEB)

    Martin, L., E-mail: lee.martin@ntu.ac.u [School of Science and Technology, Nottingham Trent University, Clifton Lane, Clifton, Nottingham NG11 8BS (United Kingdom); Wallis, J.D. [School of Science and Technology, Nottingham Trent University, Clifton Lane, Clifton, Nottingham NG11 8BS (United Kingdom); Day, P. [Chemistry Department, University College London, 20 Gordon Street, London WC1H 0AJ (United Kingdom); Nakatsuji, S.-I.; Yamada, J.-I.; Akutsu, H. [Graduate School of Material Science, University of Hyogo, Kamigori-cho, Ako-gun, Hyogo 678-1297 (Japan)

    2010-06-01

    BEDT-TTF salts have been widely studied because of their ability to combine various physical properties in the same lattice. The series of salts containing tris(oxalato)metallate anions has been widely studied and has given rise to paramagnetism, ferromagnetism, superconductivity, semiconductivity, conductivity and proton conductivity. However, one property that has not been exploited fully in this family of materials is chirality.

  4. Spin-current injection and detection in κ-(BEDT-TTF2Cu[N(CN2]Br

    Directory of Open Access Journals (Sweden)

    Z. Qiu

    2015-05-01

    Full Text Available Spin-current injection into an organic semiconductor κ-(BEDT-TTF2Cu[N(CN2]Br film induced by the spin pumping from an yttrium iron garnet (YIG film. When magnetization dynamics in the YIG film is excited by ferromagnetic or spin-wave resonance, a voltage signal was found to appear in the κ-(BEDT-TTF2Cu[N(CN2]Br film. Magnetic-field-angle dependence measurements indicate that the voltage signal is governed by the inverse spin Hall effect in κ-(BEDT-TTF2Cu[N(CN2]Br. We found that the voltage signal in the κ-(BEDT-TTF2Cu[N(CN2]Br/YIG system is critically suppressed around 80 K, around which magnetic and/or glass transitions occur, implying that the efficiency of the spin-current injection is suppressed by fluctuations which critically enhanced near the transitions.

  5. Thermodynamic Properties of κ-(BEDT-TTF2X Salts: Electron Correlations and Superconductivity

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    Yasuhiro Nakazawa

    2012-06-01

    Full Text Available Heat capacity measurements of κ-(BEDT-TTF2X (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 ∆Cp/γTc of 10 K class superconductors, κ-(BEDT-TTF2Cu(NCS2 and κ-(BEDT-TTF2Cu[N(CN2]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 Tc 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 T1−1 of NMR experiments etc. The results of heat capacity measurements under high pressures are also reported.

  6. Theoretical study of the zero-gap organic conductor α-(BEDT-TTF2I3

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    Akito Kobayashi, Shinya Katayama and Yoshikazu Suzumura

    2009-01-01

    Full Text Available The quasi-two-dimensional molecular conductor α-(BEDT-TTF2I3 exhibits anomalous transport phenomena where the temperature dependence of resistivity is weak but the ratio of the Hall coefficient at 10 K to that at room temperature is of the order of 104. These puzzling phenomena were solved by predicting massless Dirac fermions, whose motions are described using the tilted Weyl equation with anisotropic velocity. α-(BEDT-TTF2I3 is a unique material among several materials with Dirac fermions, i.e. graphene, bismuth, and quantum wells such as HgTe, from the view-points of both the structure and electronic states described as follows. α-(BEDT-TTF2I3 has the layered structure with highly two-dimensional massless Dirac fermions. The anisotropic velocity and incommensurate momenta of the contact points, ±k0, originate from the inequivalency of the BEDT-TTF sites in the unit cell, where ±k0 moves in the first Brillouin zone with increasing pressure. The massless Dirac fermions exist in the presence of the charge disproportionation and are robust against the increase in pressure. The electron densities on those inequivalent BEDT-TTF sites exhibit anomalous momentum distributions, reflecting the angular dependences of the wave functions around the contact points. Those unique electronic properties affect the spatial oscillations of the electron densities in the vicinity of an impurity. A marked behavior of the Hall coefficient, where the sign of the Hall coefficient reverses sharply but continuously at low temperatures around 5 K, is investigated by treating the interband effects of the magnetic field exactly. It is shown that such behavior is possible by assuming the existence of the extremely small amount of electron doping. The enhancement of the orbital diamagnetism is also expected. The results of the present research shed light on a new aspect of Dirac fermion physics, i.e. the emergence of unique electronic properties owing to the structure

  7. Order-disorder type of charge-ordering phase transition in narrow-bandwidth compound, {alpha}'-(BEDT-TTF){sub 2}IBr{sub 2}

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    Yue, Y.; Yamamoto, K.; Nakano, C.; Uruichi, M. [Institute for Molecular Science and Graduate University for Advanced Studies, Myodaiji, Okazaki, Aichi 444-8585 (Japan); Yakushi, K., E-mail: yakushi@ims.ac.j [Institute for Molecular Science and Graduate University for Advanced Studies, Myodaiji, Okazaki, Aichi 444-8585 (Japan); Inokuchi, M. [Faculty of Science and Engineering, Tokyo University of Science Yamaguchi, 1-1-1 Daigaku-dori, Onoda, Yamaguchi 756-0884 (Japan); Hiejima, T. [Department of Nanochemistry, Tokyo Polytechnic University, 1583 Iiyama, Atsugi, Kanagawa 243-0297 (Japan); Kawamoto, A. [Department of Physics, Hokkaido University, Kita-ku, Sapporo 060-0810 (Japan)

    2010-06-01

    The kinetic energy of {alpha}'-(BEDT-TTF){sub 2}IBr{sub 2}, {alpha}-(BEDT-TTF){sub 2}I{sub 3}, and {alpha}-(BEDT-TTF){sub 2}NH{sub 4}Hg(SCN){sub 4} was estimated from the room-temperature optical conductivity measured from 50 to 30 000 cm{sup -1}. The kinetic energy of {alpha}'-(BEDT-TTF){sub 2}IBr{sub 2} was significantly smaller than that of {alpha}-(BEDT-TTF){sub 2}I{sub 3} that shows metal-insulator phase transition. A clear hysteresis was found in the magnetic susceptibility near the phase transition at around 30 K.

  8. Anisotropic thermopower of the organic metal, β-(BEDT-TTF)2I3

    DEFF Research Database (Denmark)

    Mortensen, Kell; Williams, J.M.; Wang, H.H.

    1985-01-01

    Thermopower of the ambient pressure organic superconductor β-(BEDT-TTF)2I3 has been studied. Measurements performed on, respectively, crystals of needle formed morphology and on flake-like crystals with hexagon shape showed equal thermopower results. S was measured along the a-axis as well as along...... the b′-axis. Marked anisotropy is observed in the entire temperature region studied. The temperature dependence, as represented by dS/dT, is, however, nearly isotropic. On the basis of an analysis of anisotropic thermopower we attribute the isotropic part of S to a term depending on the bond...

  9. Transport Phenomena in Multilayered Massless Dirac Fermion System α-(BEDT-TTF2I3

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    Naoya Tajima

    2012-06-01

    Full Text Available A zero-gap state with a Dirac cone type energy dispersion was discovered in an organic conductor α-(BEDT-TTF2I3 under high hydrostatic pressures. This is the first two-dimensional (2D zero-gap state discovered in bulk crystals with a layered structure. In contrast to the case of graphene, the Dirac cone in this system is highly anisotropic. The present system, therefore, provides a new type of massless Dirac fermion system with anisotropic Fermi velocity. This system exhibits remarkable transport phenomena characteristic to electrons on the Dirac cone type energy structure.

  10. Organic superconductor κ-(BEDT-TTF)2Cu(NGS)2

    International Nuclear Information System (INIS)

    This paper reports on organic superconductors which have a maximum Tc in the range of 11.0--11.1 K (midpoint of the resistance jump). The total number of organic systems is still less than 1% and the maximum Tc is less than 1/10 of that of inorganic systems. The urgent tasks for the chemists are to explore a variety of new organic superconductors, and to extend the Tc to the range of 15-20 K at least. Here an overview of the chemical and physical properties of an organic superconductor κ-(BEDT-TTF)2Cu(NCS)2, of which Tc is the maximum in the organic systems, will be described. Black shinny single crystals with distorted-hexagon-shape (3 x 2 x 0.05 mm) of κ-(BEDT-TFF)2Cu(NCS)2 (abbreviated hereafter to κ-Cu(NCS)2 salt) were prepared by the electrochemical oxidation of BEDT-TTF, typically in 1,1,2-trichloroethane in the presence of CuSCN, KSCN, and 18-crown-6 ether under a constant current of 1 μA

  11. Theoretical aspects of charge correlations in θ-(BEDT-TTF2X

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    Kazuhiko Kuroki

    2009-01-01

    Full Text Available A review is given on the theoretical studies of charge correlations in θ-(BEDT-TTF2X. Various studies show that within a purely electronic model on the θ-type lattice with on-site U and nearest neighbor Vp and Vc interactions, the diagonal stripe, c-axis three-fold, and the vertical stripe charge correlations are favored in the regime VpVc, respectively. In the realistic parameter regime of Vp~Vc, there is competition between the c-axis three fold state and diagonal stripe state. Since these are different from the experimentally observed a-axis three fold and the horizontal stripe charge correlations, additional effects have to be included in order to understand the experiments. The electron–lattice coupling, which tends to distort the lattice into the θd-type, is found to favor the horizontal stripe state, suggesting that the occurrence of this stripe ordering in the actual materials may not be of purely electronic origin. On the other hand, distant electron–electron interactions have to be considered in order to understand the a-axis three fold correlation, whose wave vector is close to the nesting vector of the Fermi surface. These studies seem to suggest that the minimal model to understand the charge correlation in θ-(BEDT-TTF2X may be more complicated than expected. Future problems regarding the competition between different types of charge correlations are discussed.

  12. Spin-current injection and detection in κ-(BEDT-TTF){sub 2}Cu[N(CN){sub 2}]Br

    Energy Technology Data Exchange (ETDEWEB)

    Qiu, Z., E-mail: qiuzy@imr.tohoku.ac.jp; Hou, D. [WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Spin Quantum Rectification Project, ERATO, Japan Science and Technology Agency, Aoba-ku, Sendai 980-8577 (Japan); Uruichi, M. [Research Center of Integrative Molecular Systems (CIMoS), Institute for Molecular Science, Okazaki 444-8585 (Japan); Uchida, K. [Spin Quantum Rectification Project, ERATO, Japan Science and Technology Agency, Aoba-ku, Sendai 980-8577 (Japan); Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); PRESTO, Japan Science and Technology Agency, Saitama 332-0012 (Japan); Yamamoto, H. M. [Research Center of Integrative Molecular Systems (CIMoS), Institute for Molecular Science, Okazaki 444-8585 (Japan); RIKEN, 2-1 Hirosawa, Wako 351-0198 (Japan); Saitoh, E. [WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Spin Quantum Rectification Project, ERATO, Japan Science and Technology Agency, Aoba-ku, Sendai 980-8577 (Japan); Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Advanced Science Research Center, Japan Atomic Energy Agency, Tokai 319-1195 (Japan)

    2015-05-15

    Spin-current injection into an organic semiconductor κ-(BEDT-TTF){sub 2}Cu[N(CN){sub 2}]Br film induced by the spin pumping from an yttrium iron garnet (YIG) film. When magnetization dynamics in the YIG film is excited by ferromagnetic or spin-wave resonance, a voltage signal was found to appear in the κ-(BEDT-TTF){sub 2}Cu[N(CN){sub 2}]Br film. Magnetic-field-angle dependence measurements indicate that the voltage signal is governed by the inverse spin Hall effect in κ-(BEDT-TTF){sub 2}Cu[N(CN){sub 2}]Br. We found that the voltage signal in the κ-(BEDT-TTF){sub 2}Cu[N(CN){sub 2}]Br/YIG system is critically suppressed around 80 K, around which magnetic and/or glass transitions occur, implying that the efficiency of the spin-current injection is suppressed by fluctuations which critically enhanced near the transitions.

  13. Coexistence of Dirac and massive carriers in α-(BEDT-TTF){sub 2}I{sub 3} under hydrostatic pressure

    Energy Technology Data Exchange (ETDEWEB)

    Navarin, Fabien; Tisserond, Emilie [Laboratoire de Physique des Solides, UMR 8502, CNRS-Université Paris-Sud, Orsay F-91405 (France); Auban-Senzier, Pascale, E-mail: pascale.senzier@u-psud.fr [Laboratoire de Physique des Solides, UMR 8502, CNRS-Université Paris-Sud, Orsay F-91405 (France); Mézière, Cécile; Batail, Patrick [MOLTECH-Anjou, UMR 6200, CNRS-Université d' Angers, Bat. K, Angers F-49045 (France); Pasquier, Claude; Monteverde, Miguel [Laboratoire de Physique des Solides, UMR 8502, CNRS-Université Paris-Sud, Orsay F-91405 (France)

    2015-03-01

    We present magnetotransport measurements of α-(BEDT-TTF){sub 2}I{sub 3} crystals under hydrostatic pressure larger than 1.5 GPa where Dirac carriers are present. We show not only the existence of high-mobility Dirac carriers but we also prove experimentally the presence of low-mobility massive carriers, in agreement with band-structure calculations.

  14. Discovery of Superconductivity in κ-(BEDT-TTF)_2Cu[N(CN)_2]I

    Science.gov (United States)

    Lee, H. S.; Cowan, D. O.; Fainchtein, R.; Bohandy, J.; Geiser, U.; Wang, H. H.; Schlueter, J. A.; Kushch, N. D.; Flynn, J. P.; Vanzile, M. L.; Williams, J. M.

    1996-03-01

    Evidence of superconductivity with a mid-point transition temperature of 7.2K was found for the first time on crystals of κ-(BEDT-TTF)_2Cu[N(CN)_2]I. The crystals were first synthesized at Johns Hopkins University and later independently synthesized at Argonne National Laboratory. The structure of the materials has been confirmed to be of the kappa-phase moiety by STM, AFM, Raman, ESR and X-ray diffraction. Superconductivity of the samples was confirmed by dc-conductivity, modulated microwave reflectance and magnetic susceptibility with a transition onset of 7.5K. (Authors HSL, DOC and RF acknowledge support by NSF under grant No. DMR-9223481; authors affiliated with ANL acknowledge support by DOE under contract No. W-31-109-ENG-38.)

  15. Effects of spin fluctuations, charge fluctuations and lattice distortions on charge orders in theta- and alpha-type BEDT-TTF salts

    Energy Technology Data Exchange (ETDEWEB)

    Miyashita, Satoshi [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Yonemitsu, Kenji, E-mail: satoshi@ims.ac.j [Institute for Molecular Science, Okazaki 444-8585 (Japan)

    2009-02-01

    Effects of spin fluctuations, charge fluctuations and lattice distortions on charge orders in theta-(BEDT-TTF){sub 2}RbZn(SCN){sub 4} and alpha-(BEDT-TTF){sub 2}I{sub 3} are investigated theoretically in a two-dimensional extended Peierls-Hubbard model. By using exact diagonalization, we have calculated hole-density distributions and transfer modulations with transfer integrals based on the corresponding high-temperature structures as a function of electron-phonon couplings. The results clearly show the origin of their lattice-effect differences, namely, the lattice effect on theta-(BEDT-TTF){sub 2}RbZn(SCN){sub 4} is much larger than that on alpha-(BEDT-TTF){sub 2}I{sub 3}. This finding is systematically explained by the strong-coupling perturbation theory. It is found that spin fluctuations induce lattice distortions in theta-(BEDT-TTF){sub 2}RbZn(SCN){sub 4}, but their effects are partially cancelled by charge fluctuations in alpha-(BEDT-TTF){sub 2}I{sub 3}.

  16. Unconventional charge density wave in the organic conductor alpha-(BEDT-TTF)_2KHg(SCN)_4

    OpenAIRE

    Maki, Kazumi; Dóra, Balázs; Kartsovnik, Mark; Virosztek, Attila; Korin-Hamzic, Bojana; Basletic, Mario

    2002-01-01

    The low temperature phase (LTP) of alpha-(BEDT-TTF)_2KHg(SCN)_4 salt is known for its surprising angular dependent magnetoresistance (ADMR), which has been studied intensively in the last decade. However, the nature of the LTP has not been understood until now. Here we analyse theoretically ADMR in unconventional (or nodal) charge density wave (UCDW). In magnetic field the quasiparticle spectrum in UCDW is quantized, which gives rise to spectacular ADMR. The present model accounts for many st...

  17. Magneto-oscillations in BEDT-TTF salts in Pulsed Magnetic Fields of up to 55 Tesla

    Science.gov (United States)

    Singleton, John

    1997-03-01

    Charge-transfer salts based on the molecule BEDT-TTF are excellent systems for high-magnetic-field studies of novel fermiological and many-body effects (G. Boebinger, Physics Today, June 1996, p36). The salts have quasi-two-dimensional Fermi surfaces, and exhibit a wide variety of low temperature groundstates; high quality crystals are available, so that phenomena such as cyclotron resonance and the de Haas-van Alphen effect may be readily observed (J. Singleton et al., Surface Science 361), 894 (1996). This presentation will report magnetisation measurements of the salts carried out in pulsed magnetic fields of up to 55 T and at temperatures down to 350 mK. These experiments reveal very strong quantum oscillations consisting of two components, de Haas-van Alphen oscillations and so-called ``eddy current resonances'', caused by the very deep minima in the resistivity which accompany the quantum Hall effect (N. Harrison et al., Phys. Rev. Lett. 77), 1576 (1996). The magnetisation studies are discussed in the context of numerical models of the magnetisation and magnetoresistance of BEDT-TTF salts (N. Harrison et al., Phys. Rev. B 54), 9977 (1996). It is found that the quantum Hall effect should indeed be present at high magnetic fields in such materials, in spite of the coexistence of quasi-one and quasi-two-dimensional Fermi surface components. Recent attempts to observe quantum Hall plateaux in magnetotransport experiments by the author and coworkers will be reviewed and evidence for the field-induced localisation of one-dimensional electrons in BEDT-TTF salts will be discussed.

  18. The temperature dependence of the reflection intensities of the modulated composite structure Hg0.776(BEDT-TTF)SCN

    International Nuclear Information System (INIS)

    The temperature dependence between 30 and 300 K of the intensities of 24 reflections of the column-composite structure Hg0.776(BEDT-TTF)SCN [Wang, Beno, Carlson, Thorup, Murray, Porter, Williams, Maly, Bu, Petricek, Cisarova, Coppens, Jung, Whangbo, Shirber and Overmyer (1991). Chem. Mater. 3, 508-513; BEDT-TTF=3,4,3',4'-bis(ethylenedithio)-2,2',5,5'-tetrathiafulvalene] has been analyzed in terms of a model including phason temperature factors. The temperature dependence of the main and first-order satellite reflections is reasonably well reproduced in a refinement with 236 observations and four variables. The results are interpreted in terms of a temperature independence of the static displacement amplitudes. The room-temperature r.m.s. phason fluctuations of the mercury sublattice are 50(2) . This value implies that the mean mercury displacement amplitude will increase by ∝60% on lowering of the temperature to within the liquid-helium range. The thermal contraction on cooling is the same for the two sublattices. (orig.)

  19. Microreflectance infrared study of electron-molecular vibrational coupling and lattice softness in BEDT-TTF salts

    Energy Technology Data Exchange (ETDEWEB)

    Ferraro, J.R.; Whangbo, Myung-Hwan [North Carolina State Univ., Raleigh, NC (United States). Dept. of Chemistry; Wang, H.H. [Argonne National Lab., IL (United States); Stout, P. [Bio-Rad, Digilab Div., Cambridge, MA (United States)

    1994-03-01

    Microreflectance infrared (MR-IR) spectra were obtained for several {beta}- and {kappa}-phase salts of bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF or ET) and its deuterium analog d{sub 8}-ET by employing polarized and unpolarized light. The vibronic region of these MR-IR spectra provides information about the electron-molecular vibration (EMV) coupling, and the highest-frequency C-C-H bending vibration observed for an ET salt reflects the extent of its lattice softness. Under polarized light, the EMV coupling for an ET salt depends strongly upon how the light polarization vector is aligned with respect to the sample crystallographic axes. The lowest vibron frequency is indicative of increased EMV coupling.

  20. Coordination Chemistry of 2,2'-Bipyridyl- and 2,2':6',2″-Terpyridyl-Substituted BEDT-TTFs: Formation of a Supramolecular Capsule Motif by the Iron(II) Tris Complex of 2,2'-Bipyridine-4-thiomethyl-BEDT-TTF.

    Science.gov (United States)

    Wang, Qiang; Martin, Lee; Blake, Alexander J; Day, Peter; Akutsu, Hiroki; Wallis, John D

    2016-09-01

    Molecules of tris(2,2'-bipyridine-4-thiomethyl-BEDT-TTF)iron(II) (BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene) assemble in pairs to form a novel supramolecular capsular structure in the solid state. Three BEDT-TTF residues from one complex lie in the three grooves between coordinated bipyridines of the other complex, and vice versa, to form a capsule with 3-fold rotational symmetry and an internal volume of ca. 160 Å(3). Further aspects of the coordination chemistry of this ligand, its 6-substituted isomer, and the 2,2':6'2″-terpyridyl-4'-thiomethyl-BEDT-TTF analogue are described.

  1. Synthesis of racemic and chiral BEDT-TTF derivatives possessing hydroxy groups and their achiral and chiral charge transfer complexes

    Directory of Open Access Journals (Sweden)

    Sara J. Krivickas

    2015-09-01

    Full Text Available Chiral molecular crystals built up by chiral molecules without inversion centers have attracted much interest owing to their versatile functionalities related to optical, magnetic, and electrical properties. However, there is a difficulty in chiral crystal growth due to the lack of symmetry. Therefore, we made the molecular design to introduce intermolecular hydrogen bonds in chiral crystals. Racemic and enantiopure bis(ethylenedithiotetrathiafulvalene (BEDT-TTF derivatives possessing hydroxymethyl groups as the source of hydrogen bonds were designed. The novel racemic trans-vic-(hydroxymethyl(methyl-BEDT-TTF 1, and racemic and enantiopure trans-vic-bis(hydroxymethyl-BEDT-TTF 2 were synthesized. Moreover, the preparations, crystal structure analyses, and electrical resistivity measurements of the novel achiral charge transfer salt θ21-[(S,S-2]3[(R,R-2]3(ClO42 and the chiral salt α’-[(R,R-2]ClO4(H2O were carried out. In the former θ21-[(S,S-2]3[(R,R-2]3(ClO42, there are two sets of three crystallographically independent donor molecules [(S,S-2]2[(R,R-2] in a unit cell, where the two sets are related by an inversion center. The latter α’-[(R,R-2]ClO4(H2O is the chiral salt with included solvent H2O, which is not isostructural with the reported chiral salt α’-[(S,S-2]ClO4 without H2O, but has a similar donor arrangement. According to the molecular design by introduction of hydroxy groups and a ClO4− anion, many intermediate-strength intermolecular hydrogen bonds (2.6–3.0 Å were observed in these crystals between electron donor molecules, anions, and included H2O solvent, which improve the crystallinity and facilitate the extraction of physical properties. Both salts are semiconductors with relatively low resistivities at room temperature and activation energies of 1.2 ohm cm with Ea = 86 meV for θ21-[(S,S-2]3[(R,R-2]3(ClO42 and 0.6 ohm cm with Ea = 140 meV for α'-[(R,R-2]2ClO4(H2O, respectively. The variety of donor arrangements

  2. Electronic transport properties and structural transformations of κ-(BEDT-TTF)2Cu[N(CN)2]I

    International Nuclear Information System (INIS)

    Formation of an insulating ground state in the salt of κ-(BEDT-TTF)2Cu[N(CN)2]I was studied by measuring the temperature dependence of the electronic transport properties (the anisotropy of the resistivity, thermopower along the principal in-plane directions, and the Hall effect) and the x-ray diffraction patterns. Qualitative agreement of all the transport properties with the metallic state predicted by the band structure calculation was found above 230 K. Transformation to the insulating state proceeds via an intermediate stage between 230 and ∼100 K, in which the transport properties are affected by localization phenomena in the disordered metallic state. The state is induced by the formation of a commensurate superstructure in the anion layer, leading to a unit cell doubling in the c-direction. The electronic spectrum starts to form a real gap below 100 K, as indicated by the sharp thermopower change, which is mainly related to the destruction of the hole pocket. The gap formation is accompanied by an in-plane resistivity anisotropy increase. This transformation is due to a short-range ordering, with a wave vector close to c*/3, strongly interacting with the electronic system

  3. Relationship between effective mass and superconducting critical temperature in the organic superconductor {kappa}-(BEDT-TTF){sub 2}Cu(NCS){sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Caulfield, J. [Physics Dept., Univ. of Oxford, Clarendon Lab. (United Kingdom); Lubczynski, W. [Physics Dept., Univ. of Oxford, Clarendon Lab. (United Kingdom); Lee, W. [School of Physics and Materials, Lancaster Univ. (United Kingdom); Singleton, J. [Physics Dept., Univ. of Oxford, Clarendon Lab. (United Kingdom); Pratt, F.L. [Physics Dept., Univ. of Oxford, Clarendon Lab. (United Kingdom); Hayes, W. [Physics Dept., Univ. of Oxford, Clarendon Lab. (United Kingdom); Kurmoo, M. [Royal Institution, London (United Kingdom); Day, P. [Royal Institution, London (United Kingdom)

    1995-03-15

    We report high pressure magnetotransport on the organic superconductor {kappa}-(BEDT-TTF){sub 2}Cu(NCS){sub 2}. The observation of Shubnikov-de Haas and magnetic breakdown oscillations has allowed the pressure dependences of the Fermi surface topology and quasiparticle effective masses to be deduced and compared with simultaneous measurements of the superconducting critical temperature T{sub c}. The data strongly suggest that the enhancement of the effective mass and the superconducting behaviour are directly connected. The results are fitted by calculations of the linearised Eliashberg equations. (orig.)

  4. Gate-Induced Thermally Stimulated Current on the Ferroelectric-like Dielectric Properties of (BEDT-TTF(TCNQ Crystalline Field Effect Transistor

    Directory of Open Access Journals (Sweden)

    Kazuhiro Kudo

    2012-06-01

    Full Text Available A gate-induced thermally stimulated current (TSC on β′-(BEDT-TTF(TCNQ crystalline FET were conducted to elucidate the previously observed ferroelectric-like behaviors. TSC which is symmetric for the polarization of an applied VPG and has a peak at around 285 K was assigned as a pyroelectric current. By integrating the pyroelectric current, temperature dependence of the remnant polarization charge was obtained and the existence of the ferroelectric phase transition at 285 K was clearly demonstrated. We have tentatively concluded that the phase transition between dimer Mott insulator and charge ordered phase occurred at around the interface of organic crystal and substrate.

  5. Effect of Hydrostatic Pressure on Superconductivity in kappa-[(BEDT-TTF)1-X(Bedse-TTF)X]2Cu[N(CN)2]Br

    OpenAIRE

    Sushko, Y. V.; Leontsev, S. O.; Korneta, O. B.; Kawamoto, A

    2005-01-01

    Static susceptibility of kappa-[(BEDT-TTF)1-x(BEDSe-TTF)x]2Cu[N(CN)2]Br alloys with the BEDSe-TTF content near the border-line of ambient pressure superconductivity (x~0.3) has been measured as a function of temperature, magnetic field, and pressure. A non-monotonic pressure dependence is observed for both the superconducting critical temperature and superconducting volume fraction, with both quantities showing growth under pressure in the initial pressure range P < 0.3 kbar. The results are ...

  6. Disorder-induced gap in the normal density of states of the organic superconductor κ-(BEDT-TTF)2Cu[N(CN)2]Br.

    Science.gov (United States)

    Diehl, Sandra; Methfessel, Torsten; Tutsch, Ulrich; Müller, Jens; Lang, Michael; Huth, Michael; Jourdan, Martin; Elmers, Hans-Joachim

    2015-07-01

    The local density of states (DOS) of the organic superconductor κ-(BEDT-TTF)2Cu[N(CN)2]Br, measured by scanning tunneling spectroscopy on in situ cleaved surfaces, reveals a logarithmic suppression near the Fermi edge persisting above the critical temperature T(c). The experimentally observed suppression of the DOS is in excellent agreement with a soft Hubbard gap as predicted by the Anderson-Hubbard model for systems with disorder. The electronic disorder also explains the diminished coherence peaks of the quasi-particle DOS below T(c).

  7. LDA+DMFT investigation of the organic charge transfer salt κ-(BEDT-TTF)2Cu[N(CN)2]Cl

    Science.gov (United States)

    Feldner, Helene; Jacko, Anthony; Rose, Eva; Dressel, Martin; Valenti, Roser; Jeschke, Harald O.

    2013-03-01

    We combine density functional theory with dynamical mean field theory for the study of organic molecular crystals using a new scheme to construct molecular Wannier functions. We calculate spectral and optical properties for the strongly correlated material κ-(BEDT-TTF)2Cu[N(CN)2]Cl. The new method allows us to analyze the contributions of intradimer and interdimer contributions to the optical conductivity on the same footing. We find in agreement with experiment that strong correlations lead to a Hubbard peak in the optical conductivity.

  8. Zeeman-driven phase transition within the superconducting state of {kappa}-(BEDT-TTF){sub 2}Cu(NCS){sub 2}.

    Energy Technology Data Exchange (ETDEWEB)

    Wright, J. A.; Green, E.; kuhns, P.; Reyes, A.; Brooks, J.; Schlueter, J.; Kato, R.; Yamamoto, H.; Kobayashi, M.; Brown , S. E. (Materials Science Division); (Univ. California-Los Angeles); (Nat. High Magnetic Field Lab.); (RIKEN)

    2011-08-16

    {sup 13}C nuclear magnetic resonance measurements were performed on {kappa}-(BEDT-TTF){sub 2}Cu(NCS){sub 2}, with the external field placed parallel to the quasi-2D conducting layers. The absorption spectrum is used to determine the electronic spin polarization M{sub s} as a function of external field H at a temperature T = 0.35 K. A discontinuity in the derivative dM{sub s}/dH at an applied field of H{sub s} = 213 {+-} 3 kOe is taken as evidence for a Zeeman-driven transition within the superconducting state and stabilization of inhomogeneous superconductivity.

  9. Coulomb enhancement of superconducting pair-pair correlations in a 3/4 -filled model for κ -(BEDT-TTF)2X

    Science.gov (United States)

    De Silva, W. Wasanthi; Gomes, N.; Mazumdar, S.; Clay, R. T.

    2016-05-01

    We present the results of precise correlated-electron calculations on the monomer lattices of the organic charge-transfer solids κ -(BEDT-TTF) 2X for 32 and 64 molecular sites. Our calculations are for band parameters corresponding to X =Cu[N (CN) 2]Cl and Cu2(CN) 3, which are semiconducting antiferromagnetic and quantum spin liquid, respectively, at ambient pressure. We have performed our calculations for variable electron densities ρ per BEDT-TTF molecule, with ρ ranging from 1 to 2. We find that d -wave superconducting pair-pair correlations are enhanced by electron-electron interactions only for a narrow carrier concentration about ρ =1.5 , which is precisely the carrier concentration where superconductivity in the charge-transfer solids occurs. Our results indicate that the enhancement in pair-pair correlations is not related to antiferromagnetic order, but to a proximate hidden spin-singlet state that manifests itself as a charge-ordered state in other charge-transfer solids. Long-range superconducting order does not appear to be present in the purely electronic model, suggesting that electron-phonon interactions also must play a role in a complete theory of superconductivity.

  10. Topological Domain Wall and Valley Hall Effect in Charge Ordered Phase of Molecular Dirac Fermion System α-(BEDT-TTF)2I3

    Science.gov (United States)

    Matsuno, Genki; Omori, Yukiko; Eguchi, Takaaki; Kobayashi, Akito

    2016-09-01

    The topological domain wall and valley Hall effect are theoretically investigated in the molecular conductor α-(BEDT-TTF)2I3. By using the mean-field theory in an extended Hubbard model, it is demonstrated under a cylinder boundary condition that a domain wall emerges in the charge ordered phase, and exhibits a topological nature near the phase transition to the massless Dirac Fermion phase. The topological nature is well characterized by the Berry curvature, which has opposite signs in two charge ordered phases divided by the domain wall, and gives rise to the valley Hall conductivity with opposite signs, enabling these phases to be distinguished. It is also found that the valley Hall conductivity in the tilted Dirac cones exhibits a characteristic double-peak structure as a function of chemical potential using the semi classical formalism.

  11. Role of layer packing for the electronic properties of the organic superconductor (BEDT-TTF ) 2Ag (CF3)4(TCE )

    Science.gov (United States)

    Altmeyer, Michaela; Valentí, Roser; Jeschke, Harald O.

    2015-06-01

    The charge-transfer compound (BEDT-TTF ) 2Ag (CF3)4(TCE ) crystallizes in three polymorphs with different alternating layers: While a phase with a κ packing motif has a low superconducting transition temperature of Tc=2.6 K , two phases with higher Tc of 9.5 and 11 K are multilayered structures consisting of α' and κ layers. We investigate these three systems within density functional theory and find that the α' layer shows different degrees of charge order for the two κ -α' systems and directly influences the electronic behavior of the conducting κ layer. We discuss the origin of the distinct behavior of the three polymorphs and propose a minimal tight-binding Hamiltonian for the description of these systems based on projective molecular Wannier functions.

  12. Vibrational Spectra of β″-Type BEDT-TTF Salts: Relationship between Conducting Property, Time-Averaged Site Charge and Inter-Molecular Distance

    Directory of Open Access Journals (Sweden)

    Takashi Yamamoto

    2012-07-01

    Full Text Available The relationship between the conducting behavior and the degree of charge fluctuation in the β″-type BEDT-TTF salts is reviewed from the standpoints of vibrational spectroscopy and crystal structure. A group of β″-type ET salts demonstrates the best model compounds for achieving the above relationship because the two-dimensional structure is simple and great diversity in conducting behavior is realized under ambient pressure. After describing the requirement for the model compound, the methodology for analyzing the results of the vibrational spectra is presented. Vibrational spectroscopy provides the time-averaged molecular charge, the charge distribution in the two-dimensional layer, and the inter-molecular interactions, etc. The experimental results applied to 2/3-filled and 3/4-filled β″-type ET salts are reported. These experimental results suggest that the conducting property, the difference in the time-averaged molecular charges between the ionic and neutral-like sites, the alternation in the inter-molecular distances and the energy levels in the charge distributions are relevant to one another. The difference in the time-averaged molecular charges, ∆ρ, is a useful criterion for indicating conducting behavior. All superconductors presented in this review are characterized as small but finite ∆ρ.

  13. Correlation Effects on Charge Order and Zero-Gap State in the Organic Conductor α-(BEDT-TTF)2I3

    Science.gov (United States)

    Tanaka, Yasuhiro; Ogata, Masao

    2016-10-01

    The effects of electron correlation in the quasi-two-dimensional organic conductor α-(BEDT-TTF)2I3 are investigated theoretically by using an extended Hubbard model with on-site and nearest-neighbor Coulomb interactions. A variational Monte Carlo method is applied to study its ground-state properties. We show that there appears a nonmagnetic horizontal-stripe charge order in which nearest-neighbor correlation functions indicate a tendency toward a spin-singlet formation on the bonds with large transfer integrals along the charge-rich stripe. Under uniaxial pressure, a first-order transition from the nonmagnetic charge order to a zero-gap state occurs. Our results on a spin correlation length in the charge-ordered state suggest that a spin gap is almost unaffected by the uniaxial pressure in spite of the suppression of the charge disproportionation. The relevance of these contrasting behaviors in spin and charge degrees of freedom to recent experimental observations is discussed.

  14. Static and dynamic interaction between π and d electrons in organic superconductor β″-(BEDT-TTF)4[(H3O ) Fe (C2O4)3] .C6H5Br studied by 13C NMR spectroscopy

    Science.gov (United States)

    Ihara, Y.; Futami, Y.; Kawamoto, A.; Matsui, K.; Goto, T.; Sasaki, T.; Benmansour, S.; Gómez-García, C. J.

    2016-08-01

    We present the results of 13C NMR experiments in an organic superconductor with localized Fe spins β″-(BEDT-TTF) 4[(H3O ) Fe (C2O4)3] .C6H5Br . We reveal the antiferromagnetic coupling between Fe d spins and π spins, which creates an exchange field antiparallel to the external field direction at the π electrons. In addition to the static effects of Fe spins, we show from the nuclear spin-lattice relaxation rate measurement that the magnetic fluctuations generated by Fe spins are suppressed at low temperatures and high magnetic fields. These conditions are suitable to stabilize the field-induced superconductivity by the field compensation mechanism. After the suppression of Fe-spin dynamics by a magnetic field of 19 T, we observed the underlying π -electron contribution. We discuss a possible anomaly in the π -electron system.

  15. Infrared and Raman studies of {alpha}-(BEDT-TTF){sub 2}MHg(SCN){sub 4} with M=NH{sub 4} and K at low temperature: Breaking of inversion symmetry due to charge-ordering fluctuation

    Energy Technology Data Exchange (ETDEWEB)

    Hiejima, T., E-mail: hiejima@nano.t-kougei.ac.j [Department of Nanochemistry, Faculty of Engineering, Tokyo Polytechnic University, 1583, Iiyama, Atsugi (Japan); Yamada, S. [Department of Nanochemistry, Faculty of Engineering, Tokyo Polytechnic University, 1583, Iiyama, Atsugi (Japan); Uruichi, M.; Yakushi, K. [Institute for Molecular Science, National Institutes of Natural Science, 38, Nichigo-naka, Myodaiji, Okazaki (Japan)

    2010-06-01

    The infrared and Raman spectra were measured on the edge plane of the single crystals of quasi-two-dimensional organic conductors {alpha}-(BEDT-TTF){sub 2}MHg(SCN){sub 4}(M=NH{sub 4} and K) to look for experimental evidence for the charge-ordering fluctuation. In the optical conductivity spectra for K-salt, four charge sensitive {nu}{sub 27} modes, three of which are infrared active when inversion symmetry exists, were found at around 200 K. From the simple symmetry consideration, the finding of four {nu}{sub 27} modes gives evidence for the breaking of inversion symmetry, which is probably associated to charge-ordering fluctuation. In contrast, NH{sub 4}-salt was found to keep the inversion symmetry down to 7.3 K.

  16. The role of magnetic ions on the magnetotransport properties of the charge-transfer salts {beta}''-BEDT-TTF{sub 4}[(H{sub 3}O)M(C{sub 2}O{sub 4}){sub 3}]C{sub 5}H{sub 5}N where M=Ga{sup 3+}, Cr{sup 3+} or Fe{sup 3+}

    Energy Technology Data Exchange (ETDEWEB)

    Coldea, A.I. E-mail: a.coldea1@physics.ox.ac.uk; Bangura, A.F.; Singleton, J.; Ardavan, A.; Akutsu-Sato, A.; Akutsu, H.; Turner, S.; Day, P

    2004-05-01

    We report high-field magnetotransport measurements on {beta}''-BEDT-TTF{sub 4}[(H{sub 3}O)M(C{sub 2}O{sub 4}){sub 3}]C{sub 5}H{sub 5}N, where M=Ga{sup 3+}, Cr{sup 3+} or Fe{sup 3+}. In spite of the differing M ions, these compounds have very similar Fermi surfaces. We observe four distinct Shubnikov-de Haas frequencies, corresponding to four Fermi-surface pockets; the frequencies exhibit the additive relationship expected for a compensated semimetal. The compounds show paramagnetic behaviour and no superconductivity down to 0.5 K, in contrast to other materials of the same family with different solvent molecules.

  17. Magnetic field, frequency and temperature dependence of complex conductance of ultrathin La1.65Sr0.45CuO4/La2CuO4 films and the organic superconductors κ-(BEDT-TTF)2Cu[N(CN)2]Br

    Science.gov (United States)

    Gasparov, V. A.; He, Xi; Dubuis, G.; Pavuna, D.; Kushch, N. D.; Yagubskii, E. B.; Schlueter, J. A.; Bozovic, I.

    2015-09-01

    We used atomic-layer molecular beam epitaxy (ALL-MBE) to synthesize bilayer films of a cuprate metal (La1.65Sr0.45CuO4, LSCO) and a cuprate insulator (La2CuO4, LCO), in which interface superconductivity occurs in a layer that is just one-half unit cell thick. We have studied the magnetic field and temperature dependence of the complex sheet conductance, σ(ω), of these films, and compared them to κ-(BEDT-TTF)2Cu[N(CN)2]Br single crystals. The magnetic field H was applied both parallel and perpendicular to the 2D conducting layers. Experiments have been carried out at frequencies between 23 kHz and 50 MHz using either two-coil mutual inductance technique, or the LC resonators with spiral or rectangular coils. The real and the imaginary parts of the mutual-inductance M(T,ω) between the coil and the sample were measured and converted to complex conductivity. For H perpendicular to the conducting layers, we observed almost identical behavior in both films and κ-Br single crystals: (i) the transition onset in the inductive response, Lk-1(T) occurs at a temperature lower by 2 K than in Reσ(T), (ii) this shift is almost constant with magnetic field up to 8 T; (iii) the vortex diffusion constant D(T) is exponential due to pinning of vortex cores. These results can be described by the extended dynamic theory of the Berezinski-Kosterlitz-Thouless (BKT) transition and dynamics of bound vortex-antivortex pairs with short separation lengths.

  18. Organic charge transfer phase formation in thin films of the BEDT-TTF/TCNQ donor-acceptor system

    DEFF Research Database (Denmark)

    Solovyeva, Vita; Keller, K.; Huth, M.

    2009-01-01

    room temperature and analyzed the layer structures by optical microscopy, X-ray diffraction and focused ion beam cross sectioning before and after annealing. We found clear evidence for the formation of a charge transfer phase during the annealing procedure. For the as-grown samples we could not detect...

  19. Unveiling the microscopic nature of correlated organic conductors: the case of kappa-(BEDT-TTF)2Cu[N(CN)2]BrxCl1-x

    OpenAIRE

    Ferber, Johannes; Foyevtsova, Kateryna; Jeschke, Harald O.; Valenti, Roser

    2012-01-01

    A few organic conductors show a diversity of exciting properties like Mott insulating behaviour, spin liquid, antiferromagnetism, bad metal or unconventional superconductivity controlled by small changes in temperature, pressure or chemical substitution. While such a behaviour can be technologically relevant for functional switches, a full understanding of its microscopic origin is still lacking and poses a challenge in condensed matter physics since these phases may be a manifestation of ele...

  20. Ultrafast THz response of photo-induced insulator to metal transition in charge ordered organic conductor alpha-(BEDT-TTF){sub 2}I{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Nakaya, H; Takahashi, Y [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); Yamamoto, K; Yakushi, K [Institute for Molecular Science, Okazaki, 444-8585 (Japan); Saito, S [Institute of Information and Communications Technology, Kobe, 651-2492 (Japan); Iwai, S, E-mail: s.iwai@sspp.phys.tohoku.ac.j

    2009-02-01

    Photo-induced insulator to metal transition in a two-dimensional charge-ordered (CO) organic salt alpha-(ET){sub 2}I{sub 3} (ET: [bis(ethylenedithio)]tetrathiafulvalene) was investigated using near-IR-pump and terahertz(THz)-probe spectroscopy. Electronic properties and electron-phonon (e-p) coupling of the photo-induced metallic state were discussed based on the excitation intensity and temperature dependences of transient absorption spectrum. Long-lived (ca. ns) induced absorption with large spectral weight at < 5 meV is detected for strong excitation at T{approx}T{sub CO} (T{sub CO}=135 K), which is attributable to the photo-induced macroscopic metallic state. On the other hand, short-lived transient absorption, reflecting generation of the microscopic metallic state, shows relatively small spectral weight for <5 meV at 20 K<

  1. Organic light-emitting devices with an n-type bis(ethylenedithio)-tetrathiafulvalene-doped 4,7-diphenyl-1,10-phenanthroline electron transport layer operating at low voltage

    Energy Technology Data Exchange (ETDEWEB)

    Lee, K.S.; Kim, D.H.; Lee, D.U.; Kim, T.W., E-mail: twk@hanyang.ac.kr

    2012-10-30

    The electrical and optical properties of organic light-emitting devices (OLEDs) with bis(ethylenedithio)-tetrathiafulvalene (BEDT-TTF)-doped 4,7-diphenyl-1,10-phenanthroline (BPhen) electron transport layers (ETLs) were investigated. The current density-voltage characteristics of the OLEDs with BEDT-TTF-doped BPhen ETLs and electron only devices with BEDT-TTF-doped BPhen layers showed that the electrons injected from the cathode were increased by inserting a BEDT-TTF-doped BPhen layer. OLEDs containing BEDT-TTF-doped BPhen layers at a doping concentration of 1 wt.% demonstrated the highest current density and luminance values. Enhancements of the electron injection and luminance as well as a decrease in the operating voltage of the OLEDs were achieved by inserting a BEDT-TTF-doped BPhen layer.

  2. High-frequency magneto-conductivity studies of low-dimensional organic conductors

    CERN Document Server

    Schrama, J M

    2000-01-01

    Chapter 5 I report two studies of the angle dependence of FTRs in the high-frequency magneto-conductivity. The FTRs in kappa-(BEDT-TTF) sub 2 Cu(NCS) sub 2 and alpha-(BEDT- TTF) sub 2 KHg(SCN) sub 4 show two previously unknown corrugations in the Q1D Fermi-surface sections of the two materials. The FTRs in alpha-(BEDT-TTF) sub 2 KHg(SCN) sub 4 are investigated both in the density-wave state and near its collapse into a high-temperature, high-field state. In Chapter 6 a study of the millimetre-wave properties of (TMTSF) sub 2 ClO sub 4 at low temperatures is described. Finally, in Chapter 7 I present a study of the angle dependence of the superconductor order parameter in kappa-(BEDT-TTF) sub 2 Cu(NCS) sub 2 with a new millimetre-wave technique. In this thesis I present experimental studies of the millimetre-wave magneto-conductivity of the organic charge-transfer salts kappa-(BEDT-TTF) sub 2 Cu(NCS) sub 2 , alpha-(BEDT-TTF sub 2 KHg(SCN) sub 4 and (TMTSF) sub 2 ClO sub 4. A rotating resonant cavity insert was...

  3. Study of specific heat of organic superconductors with the help of microscopic theory

    International Nuclear Information System (INIS)

    We have developed a microscopic theory of organic superconductors with Green's function technique and equation of motion method. Self-consistent equations for superconducting order parameters (Δ) have been derived. Expressions of Correlation function in both cases (Dielectrised and Non-Dielectrised cases) have been derived. Expressions for Specific heat Cse, for the Organic Superconductors have also been obtained. The theory so developed have been applied to study the interplay of superconductivity and ferromagnetism for k-(BEDT-TTF)2I3 system. These results reveal that superconductivity and SDW state coexist in k-(BEDT-TTF)2I3 salt with a layered crystal structure. (author)

  4. Electronic structure of some β-(C10H8S8)2X compounds as studied by infrared spectroscopy

    DEFF Research Database (Denmark)

    Jacobsen, Claus Schelde; Tanner, D. B.; Williams, Jack M.;

    1987-01-01

    Polarized reflectance measurements have been made on two isostructural conducting compounds of bis(ethylenedithio)tetrathiafulvalene [BEDT-TTF or ET, (C10H8S8)]: β-(ET)2AuI2 and β-(ET)2I2Br. The former is superconducting at ambient pressure with Tc=5 K, whereas the latter retains normal-metal con...

  5. TTF/TCNQ-based thin films and microcrystals. Growth and charge transport phenomena

    Energy Technology Data Exchange (ETDEWEB)

    Solovyeva, Vita

    2011-05-26

    The thesis adresses several problems related to growth and charge transport phenomena in thin films of TTF-TCNQ and (BEDT-TTF)TCNQ. The following main new problems are addressed: - The influence of thin-film specific factors, such as the substrate material and growth-induced defects, on the Peierls transition temperature in TTF-TCNQ thin films was studied; - finite-size effects in TTF-TCNQ were investigated by considering transport properties in TTF-TCNQ microcrystals. The influence of the size of the crystal on the Peierls transition temperature was studied. In this context a new method of microcontact fabrication was employed to favor the measurements; - an analysis of radiation-induced defects in TTF-TCNQ thin films and microcrystals was performed. It was demonstrated than an electron beam can induce appreciable damage to the sample such that its electronic properties are strongly modified; - a bilayer growth method was established to fabricate (BEDT-TTF)TCNQ from the gas phase. This newly developed bilayer growth method was showed to be suitable for testing (BEDT-TTF)TCNQ charge-transfer phase formation; - the structure of the formed (BEDT-TTF)TCNQ charge-transfer compounds was analyzed by using a wide range of experimental techniques. An overview and the description of the basic physical principles underlying charge-transfer compounds is given in chapter 2. Experimental techniques used for the growth and characterization of thin films and microcrystals are presented in chapter 3. Chapter 4 gives an overview of the physical properties of the studied organic materials. Chapter 5 discussed the experimental study of TTF-TCNQ thin films. he Peierls transition in TTF-TCNQ is a consequence of the quasi-one-dimensional structure of the material and depends on different factors, studied in chapters 5 and 6. In contradistinction to TTF-TTCNQ, the (BEDT-TTF)TCNQ charge-transfer compound crystallizes in several different modifications with different physical properties

  6. Antiferromagnetic fluctuations in a quasi-two-dimensional organic superconductor detected by Raman spectroscopy.

    Energy Technology Data Exchange (ETDEWEB)

    Drichko, Natalia; Hackl, Rudi; Schlueter, John A.

    2015-10-15

    Using Raman scattering, the quasi-two-dimensional organic superconductor kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]Br (T-c = 11.8 K) and the related antiferromagnet kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]Cl are studied. Raman scattering provides unique spectroscopic information about magnetic degrees of freedom that has been otherwise unavailable on such organic conductors. Below T = 200 K a broad band at about 500 cm(-1) develops in both compounds. We identify this band with two-magnon excitation. The position and the temperature dependence of the spectral weight are similar in the antiferromagnet and in the metallic Fermi liquid. We conclude that antiferromagnetic correlations are similarly present in the magnetic insulator and the Fermi-liquid state of the superconductor.

  7. Photoinduced melting and charge order in quarter-filled organic conductors: Itinerant electron systems with competing interactions

    Energy Technology Data Exchange (ETDEWEB)

    Yonemitsu, Kenji; Tanaka, Yasuhiro; Miyashita, Satoshi [Institute for Molecular Science, Okazaki 444-8585 (Japan); Maeshima, Nobuya, E-mail: kxy@ims.ac.j [Institute of Materials Science, University of Tsukuba, Tsukuba 305-8573 (Japan)

    2009-02-01

    Photoinduced charge dynamics in one- and two-dimensional organic conductors are studied theoretically in extended Peierls-Hubbard models. For quasi-one-dimensional (EDO-TTF){sub 2}PF{sub 6}, photoinduced change in the charge order pattern from (0110) to (1010) is accompanied by probe-energy-dependent oscillations of conductivity. This is caused by coexistence of charge order and delocalized electrons. For quasi-two-dimensional alpha-(BEDT-TTF){sub 2}I{sub 3} and theta-(BEDT-TTF){sub 2}RbZn(SCN){sub 4}, photoinduced melting of the horizontal-stripe charge order proceeds easier in the alpha-type salt than in the theta-type salt. This is because the charge order in the theta-type salt is more strongly stabilized by electron-phonon interactions.

  8. Magnetic Field-Induced Superconductor-Insulator-Metal Transition in an Organic Conductor: An Infrared Magneto-Optical Imaging Spectroscopy

    OpenAIRE

    Nishi, Tatsuhiko; Kimura, Shin-ichi; Takahashi, Toshiharu; Im, Hojun; Kwon, Yong-seung; Ito, Takahiro; Miyagawa, Kazuya; Taniguchi,Hiromi; Kawamoto, Atsushi; Kanoda, Kazushi

    2006-01-01

    The magnetic field-induced superconductor-insulator-metal transition (SIMT) in partially deuterated $\\kappa$-(BEDT-TTF)$_2$Cu[N(CN)$_2$]Br, which is just on the Mott boundary, has been observed using the infrared magneto-optical imaging spectroscopy. The infrared reflectivity image on the sample surface revealed that the metallic (or superconducting) and insulating phases coexist and they have different magnetic field dependences. One of the magnetic field dependence is SIMT that appeared on ...

  9. Coulomb interaction effect in tilted Weyl fermion in two dimensions

    OpenAIRE

    Isobe, Hiroki; Nagaosa, Naoto

    2015-01-01

    Weyl fermions with tilted linear dispersions characterized by several different velocities appear in some systems including the quasi-two-dimensional organic semiconductor $\\alpha$-(BEDT-TTF)$_2$I$_3$ and three-dimensional WTe$_2$. The Coulomb interaction between electrons modifies the velocities in an essential way in the low-energy limit, where the logarithmic corrections dominate. Taking into account the coupling to both the transverse and longitudinal electromagnetic fields, we derive the...

  10. Attractive mechanical properties of a lightweight highly sensitive bi layer thermistor: polycarbonate/organic molecular conductor

    Science.gov (United States)

    Laukhina, E.; Lebedev, V.; Rovira, C.; Laukhin, V.; Veciana, J.

    2016-03-01

    The paper covers some of the basic mechanical characteristics of a recently developed bi layer thermistor: polycarbonate/(001) oriented layer of organic molecular conductor α’-(BEDT-TTF)2IxBr3-x, were BEDT-TTF=bis(ethylenedithio)tetrathiafulvalen. The nano and macro mechanical properties have been studied in order to use this flexible, low cost thermistor in sensing applications by proper way. The nano-mechanical properties of the temperature sensitive semiconducting layer of α’-(BEDT-TTF)2IxBr3-x were tested using nanoindentation method. The value of Young's modulus in direction being perpendicular to the layer plan was found as 9.0 ±1.4 GPa. The macro mechanical properties of the thermistor were studied using a 5848 MicroTester. The tensile tests showed that basic mechanical characteristics of the thermistor are close to those of polycarbonate films. This indicates a good mechanical strength of the developed sensor. Therefore, the thermistor can be used in technologies that need to be instrumented with highly robustness lightweight low cost temperature sensors. The paper also reports synthetic details on fabricating temperature sensing e-textile. As the temperature control is becoming more and more important in biomedical technologies like healthcare monitoring, this work strongly contributes on the ongoing research on engineering sensitive conducting materials for biomedical applications.

  11. Conductivity anisotropy helps to reveal the microscopic structure of a density wave at imperfect nesting

    Energy Technology Data Exchange (ETDEWEB)

    Grigoriev, P.D., E-mail: grigorev@itp.ac.ru [L.D. Landau Institute for Theoretical Physics, Chernogolovka 142432 (Russian Federation); Institut Laue-Langevin, Grenoble (France); Kostenko, S.S. [Institute of Problems of Chemical Physics, 142432 Chernogolovka (Russian Federation)

    2015-03-01

    Superconductivity or metallic state may coexist with density wave ordering at imperfect nesting of the Fermi surface. In addition to the macroscopic spatial phase separation, there are, at least, two possible microscopic structures of such coexistence: (i) the soliton-wall phase and (ii) the ungapped Fermi-surface pockets. We show that the conductivity anisotropy allows us to distinguish these two microscopic density-wave structures. The results obtained may help to analyze the experimental observations in layered organic metals (TMTSF){sub 2}PF{sub 6}, (TMTSF){sub 2}ClO{sub 4}, α-(BEDT-TTF){sub 2}KHg(SCN){sub 4} and in other compounds.

  12. Near-degeneracy of extended s +dx2-y2 and dx y order parameters in quasi-two-dimensional organic superconductors

    Science.gov (United States)

    Guterding, Daniel; Altmeyer, Michaela; Jeschke, Harald O.; Valentí, Roser

    2016-07-01

    The symmetry of the superconducting order parameter in quasi-two-dimensional bis-ethylenedithio-tetrathiafulvalene (BEDT-TTF) organic superconductors is a subject of ongoing debate. We report ab initio density-functional-theory calculations for a number of organic superconductors containing κ -type layers. Using projective Wannier functions, we derive the parameters of a common low-energy Hamiltonian based on individual BEDT-TTF molecular orbitals. In a random-phase approximation spin-fluctuation approach, we investigate the evolution of the superconducting pairing symmetry within this model, and we point out a phase transition between extended s +dx2-y2 and dx y symmetry. We discuss the origin of the mixed order parameter and the relation between the realistic molecule description and the widely used dimer approximation. Based on our ab initio calculations, we position the investigated materials in the obtained molecule model phase diagram, and we simulate scanning tunneling spectroscopy experiments for selected cases. Our calculations show that many κ -type materials lie close to the phase-transition line between the two pairing symmetry types found in our calculation, possibly explaining the multitude of contradictory experiments in this field.

  13. Anisotropic superconductivity in {beta}-(BDA-TTP){sub 2}SbF{sub 6}: STM spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Nomura, K. [Department of Physics, Hokkaido University, Sapporo 060-0810 (Japan)], E-mail: knmr@phys.sci.hokudai.ac.jp; Muraoka, R.; Matsunaga, N. [Department of Physics, Hokkaido University, Sapporo 060-0810 (Japan); Ichimura, K. [Division of Applied Physics, Hokkaido University, Sapporo 060-8628 (Japan); Yamada, J. [Division of Material Science, University of Hyogo, Hyogo 678-1297 (Japan)

    2009-03-01

    We have investigated the gap symmetry in the superconducting phase of {beta}-(BDA-TTP){sub 2}SbF{sub 6} with use of the scanning tunneling microscope (STM). The tunneling spectra obtained on the conducting surface show a clear superconducting gap structure. Its functional form is of V-shaped similarly to {kappa}-(BEDT-TTF){sub 2}X and suggests the anisotropic superconducting gap with line nodes. For lateral surfaces the shape of tunneling spectra varies from the U-shape with relatively large gap to the V-shape with small gap depending on the tunneling direction alternately twice between directional angle 0 and {pi}. From the analysis of conductance curve taking the k dependence of the tunneling probability into account, it is found that the gap has maximum near the a* and c* axes and the nodes appear along near a*+c* and the a-c* directions. These indicate that the d{sub x{sup 2}-y{sup 2}} like superconducting pair is formed in this system as the case of {kappa}-(BEDT-TTF){sub 2}X. This node direction is consistent with the theoretical prediction based on the spin fluctuation mechanism. However, the zero-bias conductance peak has not been observed yet.

  14. Millimetre-wave magneto-optical studies of systems with reduced dimensionality

    CERN Document Server

    Rzepniewski, E J

    2001-01-01

    branches are found, which arise from the complicated nature of the band dispersion in this metal. In Chapter 5, a resonant absorption of microwaves is observed in the superconducting state of kappa-(BEDT-TTF) sub 2 Cu(NCS) sub 2 and interpreted as a Josephson Plasma Resonance. The superconducting to normal transition is studied as a function of temperature and provides information about the temperature dependence of the upper critical field in kappa-(BEDT-TTF) sub 2 Cu(NCS) sub 2. Chapter 6 presents measurements of electron paramagnetic resonance in the quasi-two dimensional Heisenberg antiferromagnet Cs sub 2 CuCl sub 4. The evolution of the magnetic resonance absorption between the high temperature region (the paramagnetic regime) and temperatures below T sub N (the antiferromagnetic regime), is studied for a range of crystal orientations. At temperatures considerably higher than T sub N , the magneto-optical data show the onset of short-range spin correlations. Experimental studies of the magneto-optical r...

  15. Superconductivity in Layered Organic Metals

    Directory of Open Access Journals (Sweden)

    Jochen Wosnitza

    2012-04-01

    Full Text Available In this short review, I will give an overview on the current understanding of the superconductivity in quasi-two-dimensional organic metals. Thereby, I will focus on charge-transfer salts based on bis(ethylenedithiotetrathiafulvalene (BEDT-TTF or ET for short. In these materials, strong electronic correlations are clearly evident, resulting in unique phase diagrams. The layered crystallographic structure leads to highly anisotropic electronic as well as superconducting properties. The corresponding very high orbital critical field for in-plane magnetic-field alignment allows for the occurrence of the Fulde–Ferrell– Larkin–Ovchinnikov state as evidenced by thermodynamic measurements. The experimental picture on the nature of the superconducting state is still controversial with evidence both for unconventional as well as for BCS-like superconductivity.

  16. Coulomb Interaction Effect in Weyl Fermions with Tilted Energy Dispersion in Two Dimensions.

    Science.gov (United States)

    Isobe, Hiroki; Nagaosa, Naoto

    2016-03-18

    Weyl fermions with tilted linear dispersions characterized by several different velocities appear in some systems including the quasi-two-dimensional organic semiconductor α-(BEDT-TTF)_{2}I_{3} and three-dimensional WTe_{2}. The Coulomb interaction between electrons modifies the velocities in an essential way in the low-energy limit, where the logarithmic corrections dominate. Taking into account the coupling to both the transverse and longitudinal electromagnetic fields, we derive the renormalization group equations for the velocities of the tilted Weyl fermions in two dimensions, and found that they increase as the energy decreases and eventually hit the speed of light c to result in the Cherenkov radiation. Especially, the system restores the isotropic Weyl cone even when the bare Weyl cone is strongly tilted and the velocity of electrons becomes negative in certain directions. PMID:27035318

  17. A Mechanism of DC-AC Conversion in the Organic Thyristor

    Directory of Open Access Journals (Sweden)

    Takehiko Mori

    2010-03-01

    Full Text Available The charge ordered organic salt θ-(BEDT-TTF2CsZn(SCN4 exhibits a giant nonlinear conduction at low temperatures. The voltage-current characteristics of this compound are similar to those of a thyristor device, after which we named it the organic thyristor. This material shows current oscillation in the presense of dc voltage, which arises from a mechanism different from conventional oscillating circuits, because the oscillation appears in a sample that does not show negative derivative resistance. We have performed a standard circuit analysis, and show that the voltage-current curve is “blurred” in the high current region, and the oscillation occurs in the blurred region. This type of oscillation has never been reported, and a possible origin for this is suggested.

  18. Quantum melting of magnetic order in an organic dimer Mott-insulating system

    Science.gov (United States)

    Naka, Makoto; Ishihara, Sumio

    2016-05-01

    Quantum entanglement effects between the electronic spin and charge degrees of freedom are examined in an organic molecular solid, termed a dimer Mott-insulating system, in which molecular dimers are arranged in a crystal as fundamental units. A low energy effective model includes an antisymmetric exchange interaction, as one of the dominant magnetic interactions. This interaction favors a 90 deg spin configuration, and competes with the Heisenberg-type exchange interaction. Stabilities of the magnetic ordered phases are examined by using the spin-wave theory, as well as the Schwinger-boson theory. It is found that the spin-charge interaction promotes an instability of the long-range magnetic ordered state around a parameter region where two spin-spiral phases are merged. Implication for the quantum spin liquid state observed in κ -(BEDT-TTF)2Cu2 (CN) 3 is discussed.

  19. Synthesis, Structural Characterization of TTM-TTF Intercalated with Lamellar MnPS3

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xuan; CHEN Xing-Guo; FU Yang; SU Xu; QIN Jin-Gui

    2003-01-01

    @@ Intercalation of organic species into layer inorganic solids provides a useful approach to creating ordered organ ic-inorganic nanocomposite materials with novel properties compared with the parent compounds, and hence has attracted much attention in recent years. [1] Clement and co-workers had reported that an organic electron donor TTF monocation intercalated into the MPS3 (M = Mn, Fe), and the intercalates exhibited much higher conductivity than the corresponding pure host compounds. Our group also synthesized the intercalation compound of BEDT-TTF into MnPS3, which exhibits the room temperature conductivity of 8.5 × 10-5 S/cm, 1O5 times higher than that of the pristine MnPS3 ( < 10- 10 S/cm). [2

  20. Photoinduced melting of charge order in quasi-two-dimensional organic conductors

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, Yasuhiro; Yonemitsu, Kenji, E-mail: yasuhiro@ims.ac.j [Institute for Molecular Science, Okazaki, Aichi 444-8585 (Japan)

    2009-02-01

    Photoinduced melting of charge order in quasi-two-dimensional organic conductors alpha-(ET){sub 2}I{sub 3} (ET=BEDT-TTF) and theta-(ET){sub 2}RbZn(SCN){sub 4} is investigated theoretically. By solving the time-dependent Schroedinger equation numerically within the Hartree-Fock approximation for an extended Peierls-Hubbard model, we study the photoinduced dynamics in each compound. The obtained charge, spin and lattice dynamics are considered to reflect the different natures of charge ordered states in these systems. In particular, the melting of charge order needs more energy for theta-(ET){sub 2}RbZn(SCN){sub 4} than for alpha-(ET){sub 2}I{sub 3}, which is a consequence of large lattice distortion and the essential role of electron-phonon coupling in stabilizing the charge order in theta-(ET){sub 2}RbZn(SCN){sub 4}.

  1. Coulomb Interaction Effect in Weyl Fermions with Tilted Energy Dispersion in Two Dimensions

    Science.gov (United States)

    Isobe, Hiroki; Nagaosa, Naoto

    2016-03-01

    Weyl fermions with tilted linear dispersions characterized by several different velocities appear in some systems including the quasi-two-dimensional organic semiconductor α -(BEDT -TTF )2I3 and three-dimensional WTe2 . The Coulomb interaction between electrons modifies the velocities in an essential way in the low-energy limit, where the logarithmic corrections dominate. Taking into account the coupling to both the transverse and longitudinal electromagnetic fields, we derive the renormalization group equations for the velocities of the tilted Weyl fermions in two dimensions, and found that they increase as the energy decreases and eventually hit the speed of light c to result in the Cherenkov radiation. Especially, the system restores the isotropic Weyl cone even when the bare Weyl cone is strongly tilted and the velocity of electrons becomes negative in certain directions.

  2. Coulomb interaction effect in tilted Weyl fermion in two dimensions

    Science.gov (United States)

    Isobe, Hiroki; Nagaosa, Naoto

    Weyl fermions with tilted linear dispersions characterized by several different velocities appear in some systems including the quasi-two-dimensional organic semiconductor α-(BEDT-TTF)2I3 and three-dimensional WTe2. The Coulomb interaction between electrons modifies the velocities in an essential way in the low energy limit, where the logarithmic corrections dominate. Taking into account the coupling to both the transverse and longitudinal electromagnetic fields, we derive the renormalization group equations for the velocities of the tilted Weyl fermions in two dimensions, and found that they increase as the energy decreases and eventually hit the velocity of light c to result in the Cherenkov radiation. Especially, the system restores the isotropic Weyl cone even when the bare Weyl cone is strongly tilted and the velocity of electrons becomes negative in certain directions.

  3. Organic donor-acceptor thin film systems. Towards optimized growth conditions

    Energy Technology Data Exchange (ETDEWEB)

    Keller, Kerstin Andrea

    2009-06-30

    In this work the preparation of organic donor-acceptor thin films was studied. A chamber for organic molecular beam deposition was designed and integrated into an existing deposition system for metallic thin films. Furthermore, the deposition system was extended by a load-lock with integrated bake-out function, a chamber for the deposition of metallic contacts via stencil mask technique and a sputtering chamber. For the sublimation of the organic compounds several effusion cells were designed. The evaporation characteristic and the temperature profile within the cells was studied. Additionally, a simulation program was developed, which calculates the evaporation characteristics of different cell types. The following processes were integrated: evaporation of particles, migration on the cell walls and collisions in the gas phase. It is also possible to consider a temperature gradient within the cell. All processes can be studied separately and their relative strength can be varied. To verify the simulation results several evaporation experiments with different cell types were employed. The thickness profile of the prepared thin films was measured position-dependently. The results are in good agreement with the simulation. Furthermore, the simulation program was extended to the field of electron beam induced deposition (EBID). The second part of this work deals with the preparation and characterization of organic thin films. The focus hereby lies on the charge transfer salt (BEDT-TTF)(TCNQ), which has three known structure variants. Thin films were prepared by different methods of co-evaporation and were studied with optical microscopy, X-ray diffraction and energy dispersive X-ray spectroscopy (EDX).The formation of the monoclinic phase of (BEDT-TTF)(TCNQ) could be shown. As a last part tunnel structures were prepared as first thin film devices and measured in a He{sub 4} cryostat. (orig.)

  4. Fluctuation spectroscopy in organic charge transfer salts

    International Nuclear Information System (INIS)

    Quasi-twodimensional organic charge-transfer salts show certain analogies to the High-Temperature Cuprate Superconductors (HTSC), e.g., the layered structure where conducting and insulating sheets do alternate as well as the direct proximity of the antiferromagnetic insulating ground state to the superconducting phase. At higher temperatures the formation of a pseudo-gap in the density of states is discussed also. In contrast to the HTSC the electronic properties of the organic charge-transfer salts can be easily influenced by external parameters such as hydrostatic or chemical pressure - in a generalized phase diagram the usage of different anions X can be mapped on the axis W/U as well, see Sec. 4.2 - or moderate temperatures. In the quasi-twodimensional K-(BEDT-TTF)2X salts, e.g., a moderate pressure of p ∝ 250 bar is sufficient to shift the antiferromagnetic-insulating system (X=Cu[N(CN)2]Cl) to the metallic side of the phase diagram showing even superconductivity below a critical temperature of Tc ∝ 12.8 K. Doping as in the HTSC and the undesirable disorder accompanied with it is not necessary to induce a metal-to-insulator transition. Therefore the experimental requirements are more easily met in this class of materials compared to other strongly correlated electron systems. All this makes the organic charge-transfer salts ideal model systems to study fundamental concepts of theoretical solid state physics some of which have been of academical interest only so far. In this work fluctuation spectroscopy has been used for the first time to investigate the low-frequency dynamics of the TT-electron system in the quasi-twodimensional organic charge-transfer salts K-(BEDT-TTF)2X with the aim to gain information about the temperature, pressure and magnetic field dependence of the power spectral density of the resistance noise and therefore about the dynamics of the charge carrier fluctuations. Especially in the vicinity of correlation driven ordering phenomena

  5. Vortex pinning and lock-in effect in a layered superconductor with large in-plane anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Mansky, P.A.; Danner, G.; Chaikin, P.M. [Department of Physics, Princeton University, Princeton, New Jersey 08544 (United States)

    1995-09-01

    We use ac susceptibility to study the vortex pinning force anisotropy and the magnetic lock-in effect in the organic superconductor (TMTSF){sub 2}ClO{sub 4}, which is believed to have an in-plane anisotropy of {gamma}{sub {ital b}{ital a}}{similar_to}10 and a maximum out-of-plane anisotropy {gamma}{sub {ital c}{ital a}}{similar_to}100. Our measurements show only weak effects of the in-plane anisotropy. The pinning force for Josephson vortices (parallel to the conducting planes) is nearly independent of their orientation, except for a small but narrow peak (full width at half maximum {congruent}6{degree}) when the vortices are parallel to the TMTSF stacks ({ital a} axis). The pinning force initially {ital decreases} {ital as} {ital the} {ital vortices} {ital unlock} {ital from} {ital the} {ital layers}, contrary to the behavior previously observed in the organic superconductor (BEDT-TTF){sub 2}Cu(SCN){sub 2}. The lock-in threshold field is only weakly dependent on the initial angle of the Josephson vortices in the {ital ab} plane.

  6. C sub 6 sub 0 fullerene and its molecular complexes under axial and shear deformation

    CERN Document Server

    Spitsina, N G; Bashkin, I V; Meletov, K P

    2002-01-01

    We have studied the pristine C sub 6 sub 0 and its molecular complexes with the organic donors bis(ethylenedithio) tetrathiafulvalene (BEDT-TTF or ET) and tetramethyltetraselenafulvalene (TMTSF) by means of ESR and Raman spectroscopy at high pressure. The important changes in the ESR signal of C sub 6 sub 0 were observed under axial pressure combined with shear deformation. It is shown that the treatment at a anisotropic pressure of 4 GPa results in a reduction in the symmetry of the C sub 6 sub 0 molecule and the formation of radicals. Treatment of the molecular complex of (ET) sub 2 centre dot C sub 6 sub 0 at a pressure of approx 4.5 GPa and a temperature of 150 deg. C leads to the formation of C sub 6 sub 0 dimers. The Raman spectra of the molecular complex C sub 6 sub 0 centre dot TMTSF centre dot 2(CS sub 2) were measured in situ at ambient temperature and pressures up to 9.5 GPa. The pressure behaviour of the Raman peaks reveals singularity at 5.0 +- 0.5 GPa related to the softening and splitting of so...

  7. Magnetic-field dependence of the T*-anomaly in quasi-2D organic superconductors

    International Nuclear Information System (INIS)

    The family of quasi-2D superconductors κ-(BEDT-TTF)2X are model sy stems for strongly correlated low-dimensional metals. Recently, the unusual normal-conducting state - characterized by a line of anomalies T* (in the order o f 40 K) - has attracted considerable attention: a pseudo-gap behavior in analogy to the high-Tc cuprates, a crossover from an incoherent ''bad'' metal to a coherent Fermi-liquid regime, and a density-wave-type phase transition have been suggested as possible scenarios. To investigate the possibility of a magnetic origin we carried out detailed transport measurements in pulsed magnetic fields up to 60 T. For two different compounds, X=Cu[N(CN)2]Br a nd Cu(NCS)2, we observed a maximum in the relative magnetoresistance change right around T*. This indicates the significance of magnetic degrees of free dom which are coupled to the transport properties. Also, for the first time we w ere able to determine the magnetic-field dependence of T* showing a small negative shift with increasing field. We discuss the implications of our experiment al data for possible models explaining the anomalous normal-conducting state.

  8. Magnetic-field dependence of the T{sup *}-anomaly in quasi-2D organic superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Brandenburg, Jens; Das, Pintu [Max-Planck-Institut fuer Chemische Physik Fester Stoffe, Dresden (Germany); Mueller, Jens [Max-Planck-Institut fuer Chemische Physik Fester Stoffe, Dresden (Germany); Johann-Wolfgang-von-Goethe Universitaet, SFB/TR49, Frankfurt am Main (Germany); Lang, Michael [Johann-Wolfgang-von-Goethe Universitaet, SFB/TR49, Frankfurt am Main (Germany); Weickert, Franziska [Max-Planck-Institut fuer Chemische Physik Fester Stoffe, Dresden (Germany); Hochfeld-Magnetlabor Dresden, Forschunszentrum Dresden-Rossendorf, Dresden (Germany); Bartkowiak, Marek; Wosnitza, Jochen [Hochfeld-Magnetlabor Dresden, Forschunszentrum Dresden-Rossendorf, Dresden (Germany)

    2009-07-01

    The family of quasi-2D superconductors {kappa}-(BEDT-TTF){sub 2}X are model sy stems for strongly correlated low-dimensional metals. Recently, the unusual normal-conducting state - characterized by a line of anomalies T{sup *} (in the order o f 40 K) - has attracted considerable attention: a pseudo-gap behavior in analogy to the high-T{sub c} cuprates, a crossover from an incoherent ''bad'' metal to a coherent Fermi-liquid regime, and a density-wave-type phase transition have been suggested as possible scenarios. To investigate the possibility of a magnetic origin we carried out detailed transport measurements in pulsed magnetic fields up to 60 T. For two different compounds, X=Cu[N(CN){sub 2}]Br a nd Cu(NCS){sub 2}, we observed a maximum in the relative magnetoresistance change right around T{sup *}. This indicates the significance of magnetic degrees of free dom which are coupled to the transport properties. Also, for the first time we w ere able to determine the magnetic-field dependence of T{sup *} showing a small negative shift with increasing field. We discuss the implications of our experiment al data for possible models explaining the anomalous normal-conducting state.

  9. Rational design of organic superconductors through the use of the large, discrete molecular anions M(CF{sub 3}){sub 4}{sup -}(M = Cu, Ag, Au) and SO{sub 3}CF{sub 2}CH{sub 2}SF{sub 5}{sup -}

    Energy Technology Data Exchange (ETDEWEB)

    Schlueter, J.A.; Geiser, U.; Williams, J.M. [and others

    1996-10-01

    A new approach to synthesis of organic superconductors has recently been pioneered which involves the use of large discrete molecular anions as the charge-compensating entities in these charge transfer salts. The organic electron-donor molecule bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF or ET) has been electrocrystallized with the novel organometallic M(CF{sub 3}){sub 4}{sup -} (M=Cu, Ag, Au) anions in a variety of 1,1,2-trihaloethane solvents. Over 20 organic superconductors have been synthesized which can be described by (ET){sub 2}M(CF{sub 3}){sub 4}(1,1,2- trihaloethane). These solvated salts are shown to have highly anisotropic physical properties which can be tuned via modifications of each of their three molecular components: ET electron donor molecule, M(CF{sub 3}){sub 4}{sup -} anion, and neutral 1,1,2- trihaloethane solvent molecule. Superconductivity has also been observed in an ET salt containing the discrete SF{sub 5}CH{sub 2}CF{sub 2}SO{sub 3}{sup -} anion with onset temperature near 5.2 K.

  10. Rational design of organic superconductors through the use of the large, discrete molecular anions M(CF{sub 3}){sub 4}{sup -} (M = Cu, Ag, Au) and SO{sub 3}CF{sub 2}CH{sub 2}SF{sub 5}{sup -}

    Energy Technology Data Exchange (ETDEWEB)

    Schlueter, J.A. [Argonne National Lab., IL (United States). Div. of Chemistry and Materials Science; Geiser, U. [Argonne National Lab., IL (United States). Div. of Chemistry and Materials Science; Williams, J.M. [Argonne National Lab., IL (United States). Div. of Chemistry and Materials Science; Dudek, J.D. [Argonne National Lab., IL (United States). Div. of Chemistry and Materials Science; Kelly, M.E. [Argonne National Lab., IL (United States). Div. of Chemistry and Materials Science; Flynn, J.P. [Argonne National Lab., IL (United States). Div. of Chemistry and Materials Science; Wilson, R.R. [Argonne National Lab., IL (United States). Div. of Chemistry and Materials Science; Zakowicz, H.I. [Argonne National Lab., IL (United States). Div. of Chemistry and Materials Science; Sche, P.P. [Argonne National Lab., IL (United States). Div. of Chemistry and Materials Science; Naumann, D. [Koeln Univ. (Germany). Inst. fuer Anorganische Chemie; Roy, T. [Koeln Univ. (Germany). Inst. fuer Anorganische Chemie; Nixon, P.G. [Portland State Univ., OR (United States). Dept. of Chemistry; Winter, R.W. [Portland State Univ., OR (United States). Dept. of Chemistry; Gard, G.L. [Portland State Univ., OR (United States). Dept. of Chemistry

    1997-02-15

    A new approach to the synthesis of organic superconductors has recently been pioneered which involves the use of large, discrete, molecular anions as the charge-compensating entities in these charge transfer salts. The organic electron-donor molecule bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF or ET) has been electrocrystallized with the novel organometallic M(CF{sub 3}){sub 4}{sup -} (M = Cu, Ag, and Au) anions in a variety of 1,1,2-trihaloethane solvents. Over twenty organic superconductors have been synthesized which can be described by the general formula (ET){sub 2}M(CF{sub 3}){sub 4}(1,1,2-trihaloethane). These solvated salts are shown to have highly anisotropic physical properties which can be tuned via modifications of each of their three molecular components: ET electron donor molecule, M(CF{sub 3}){sub 4}{sup -} anion, and neutral 1,1,2-trihaloethane solvent molecule. Superconductivity has also been observed in an ET salt containing the discrete SF{sub 5}CH{sub 2}CF{sub 2}SO{sub 3}{sup -} anion with an onset temperature near 5.2 K. (orig.)

  11. GHz measurements of correlated electron systems in high magnetic fields

    CERN Document Server

    Edwards, R S

    2002-01-01

    This Thesis presents experiments performed on the high-frequency conductivity of materials in high magnetic fields. The angle dependence of resonances measured in the millimetre-wave absorption is studied using a rotating resonant cavity system, and the frequency dependence is measured using transmission techniques and a tuneable resonant cavity. Chapter 1 introduces the materials. These include the crystalline organic metals, the layered superconductor Sr sub 2 RUO sub 4 and the quantum Ising ferromagnet LiHoF sub 4. In Chapters 2 and 3, the necessary physics and experimental techniques for their investigation are outlined. Chapters 4 to 6 present measurements of cyclotron resonance in layered materials. Chapter 4 describes several models for the origin of cyclotron resonance harmonics, and describes the first definite measurement of the harmonics of a cyclotron resonance in an organic molecular metal, namely beta sup - (BEDT-TTF) sub 2 SF sub 5 CH sub 2 CF sub 2 SO sub 3. The angle dependence of the field p...

  12. A chiral molecular conductor: synthesis, structure, and physical properties of [ET]3[Sb2(L-tart)2].CH3CN (ET = bis(ethylendithio)tetrathiafulvalene; L-tart = (2R,3R)-(+)-tartrate).

    Science.gov (United States)

    Coronado, Eugenio; Galán-Mascarós, José R; Gómez-García, Carlos J; Murcia-Martínez, Ana; Canadell, Enric

    2004-12-13

    The salt [ET](3)[Sb(2)(L-tart)(2)].CH(3)CN (1) has been obtained by electrocrystallization of the organic donor bis(ethylendithio)tetrathiafulvalene (ET or BEDT-TTF) in the presence of the chiral anionic complex [Sb(2)(L-tart)(2)](2-) (L-tart = (2R,3R)-(+)-tartrate). This salt crystallizes in the chiral space group P2(1)2(1)2(1) (a = 11.145(2) angstroms, b = 12.848(2) angstroms, c = 40.159(14) angstroms, V = 5750.4(14) angstroms(3), Z = 4) and is formed by alternating layers of the anions and of the organic radicals in a noncentrosymmetric alpha-type packing. This compound shows a room temperature electrical conductivity of approximately 1 S.cm(-1) and semiconducting behavior with an activation energy of approximately 85 meV. Analysis of the magnetic susceptibility and band structure, however, suggests that this compound should be a narrow band gap semiconductor.

  13. Memory effect of photoinduced conductivity switching controlled by pulsed voltages in a molecular conductor

    Energy Technology Data Exchange (ETDEWEB)

    Iimori, Toshifumi; Ohta, Nobuhiro [Research Institute for Electronic Science, Hokkaido University, Sapporo 001-0020 (Japan); Naito, Toshio, E-mail: nohta@es.hokudai.ac.j [Division of Chemistry, Graduate School of Science, Hokkaido University, Sapporo 060-0810 (Japan)

    2009-02-01

    Transient photoresponses of the electrical conductivity in single crystals of an organic conductor alpha-(BEDT-TTF){sub 2}I{sub 3} are studied in the charge-ordered insulating phase. Electrical conductivity switching is observed in the presence of pulsed voltages and synchronous irradiation of nanosecond laser pulse. Current in the photoirradiated crystal as a function of applied voltages shows a bistability in a certain range of voltage. For the initial triggering of the conductivity switching, not only pulsed voltages but also photoirradiation is necessary. A high conductivity state produced by the switching can be repeatedly recovered by applying the pulsed voltages without further photoirradiation even after the current has been reduced to zero. This observation indicates a memory effect of the photoinduced conductivity switching. The appearance of the memory effect depends on the temporal width of the pulsed voltages, which are applied at a rate of approximately 8 Hz. In the measurement using short pulse widths, the memory effect is not observed. This controllability of the memory effect with the pulse width is related to the bistability of the current with respect to the photoirradiation intensity. The shape of the hysteresis loop appearing in the current versus photoirradiation intensity curve can be varied by changing the pulse width.

  14. Universal scaling law for the condensation energy across a broad range of superconductor classes

    Science.gov (United States)

    Kim, J. S.; Tam, G. N.; Stewart, G. R.

    2015-12-01

    One of the goals in understanding any new class of superconductors is to search for commonalities with other known superconductors. The present work investigates the superconducting condensation energy, U , in the iron based superconductors (IBSs), and compares their U with a broad range of other distinct classes of superconductor, including conventional BCS elements and compounds and the unconventional heavy fermion, S r2Ru O4 ,L i0.1ZrNCl ,κ -(BEDT-TTF)2Cu (NCS )2 , and optimally doped cuprate superconductors. Surprisingly, both the magnitude and Tc dependence (U ∝Tc3.4 ±0.2 ) of U are—contrary to the previously observed behavior of the specific heat discontinuity at Tc, Δ C —quite similar in the IBS and BCS materials for Tc>1.4 K. In contrast, the heavy fermion superconductors' U vs Tc are strongly (up to a factor of 100) enhanced above the IBS/BCS while the cuprate superconductors' U are strongly (factor of 8) reduced. However, scaling of U with the specific heat γ (or Δ C ) brings all the superconductors investigated onto one universal dependence upon Tc. This apparent universal scaling U / γ ∝Tc2 for all superconductor classes investigated, both weak and strong coupled and both conventional and unconventional, links together extremely disparate behaviors over almost seven orders of magnitude for U and almost three orders of magnitude for Tc. Since U has not yet been explicitly calculated beyond the weak coupling limit, the present results can help direct theoretical efforts into the medium and strong coupling regimes.

  15. Signatures of granular superconductivity and Josephson effects in macroscopic measurements: the case of new superconductors

    Directory of Open Access Journals (Sweden)

    S Senoussi

    2006-09-01

    Full Text Available   We report systematic investigations of the magnetic superconducting properties of the new superconducting materials (NS: New high temperature superconductors (HTS, Organic superconductors (OS, fullerenes, carbon nanotubes, MgB2 etc. We show that, contrary to conventional superconductors where the superconducting state can be coherent over several tenths of km, the macroscopic coherence range lc of the NS is often as short as 0.1 to 10 µm typically. As a consequence, the magnetic properties are dominated by granular-like effects as well as Josephson coupling between grains. Here, we concentrate on HTS ceramics and organic superconductors exclusively. In the first case we observe three distinct regimes: (i At very low field (H < 5 Oe to say all the grains are coupled via Josephson effect and lc can be considered as infinite. (2 At intermediate field (5 < H < 50 Oe, typically the grains are gradually decoupled by H and/or T. (iii At higher fields all the grains are decoupled and lc roughly coincides with the diameter of the metallurgical grains. The case of OS is more subtle and is connected with a kind of order-disorder transition that occurs in most of them. For instance, in this study, we exploit quenched disorder (after crossing such a transition in the -(BEDT-TTF2Cu[N(CN2]Br layered organic superconductor to get new insights on both the superconducting state (T £ 11.6 K and the glassy transition at Tg, by studying the superconducting properties as functions of annealing time and annealing temperature around the glassy transition. Our main result is that the data can be described by a percolation molecular cluster model in which the topology and the growth of the molecular clusters obey an Ising spin-glass-like model with Tg ≈ 80 K for the hydrogenated compound and Tg ≈ 55 K for the fully deuterated one.

  16. PREFACE: Superconducting materials Superconducting materials

    Science.gov (United States)

    Charfi Kaddour, Samia; Singleton, John; Haddad, Sonia

    2011-11-01

    and by invited authors selected by the editor. We are grateful to IUPAP, ICTP and the European Office of Aerospace Research and Development, Air Force Office of Scientific Research, United States Air Force Laboratory. We would like to acknowledge the authors for their careful work, and finally we thank Dr L Smith the publisher of Journal of Physics: Condensed Matter for her patience and help. Superconducting materials contents Raman spectrum in the pseudogap phase of the underdoped cuprates: effect of phase coherence and the signature of the KT-type superconducting transitionTao Li and Haijun Liao Pressure effects on Dirac fermions in α-(BEDT-TTF)2I3Takahiro Himura, Takao Morinari and Takami Tohyama Effect of Zn doping in hole-type 1111 phase (Pr, Sr)FeAsOXiao Lin, Chenyi Shen, Chen Lv, Jianjian Miao, Hao Tan, Guanghan Cao and Zhu-An Xu Superconductivity and ferromagnetism in EuFe2(As1 - xPx)2*Guanghan Cao, Shenggao Xu, Zhi Ren, Shuai Jiang, Chunmu Feng and Zhu'an Xu OInhomogeneous superconductivity in organic conductors: the role of disorder and magnetic fieldS Haddad, S Charfi-Kaddour and J-P Pouget

  17. Proceedings of the 9th International Symposium on Foundations of Quantum Mechanics in the Light of New Technology

    Science.gov (United States)

    Ishioka, Sachio; Fujikawa, Kazuo

    2009-06-01

    phenomena. Dynamical magnetoelectric effects in multiferroics / Y. Tokura. Exchange-stabilization of spin accumulation in the two-dimensional electron gas with Rashba-type of spin-orbit interaction / H. M. Saarikoski, G. E. W. Bauer. Electronic Aharonov-Casher effect in InGaAs ring arrays / J. Nitta, M. Kohda, T. Bergsten. Microscopic theory of current-spin interaction in ferromagnets / H. Kohno ... [et al.]. Spin-polarized carrier injection effect in ferromagnetic semiconductor / diffusive semiconductor / superconductor junctions / H. Takayanagi ... [et al.]. Low voltage control of ferromagnetism in a semiconductor P-N junction / J. Wunderlich ... [et al.].Measurement of nanosecond-scale spin-transfer torque magnetization switching / K. Ito ... [et al.]. Current-induced domain wall creep in magnetic wires / J. Ieda, S. Maekawa, S. E. Barnes. Pure spin current injection into superconducting niobium wire / K. Ohnishi, T. Kimura, Y. Otani. Switching of a single atomic spin induced by spin injection: a model calculation / S. Kokado, K. Harigaya, A. Sakuma. Spin transfer torque in magnetic tunnel junctions with synthetic ferrimagnetic layers / M. Ichimura ... [et al.]. Gapless chirality excitations in one-dimensional spin-1/2 frustrated magnets / S. Furukawa ... [et al.] -- Dirac fermions in condensed matter. Electronic states of graphene and its multi-layers / T. Ando, M. Koshino. Inter-layer magnetoresistance in multilayer massless dirac fermions system [symbol]-(BEDT-TTF)[symbol]I[symbol] / N. Tajima ... [et al.]. Theory on electronic properties of gapless states in molecular solids [symbol]-(BEDT-TTF)[symbol]I[symbol] / A. Kobayashi, Y. Suzumura, H. Fukuyama. Hall effect and diamagnetism of bismuth / Y. Fuseya, M. Ogata, H. Fukuyama. Quantum Nernst effect in a bismuth single crystal / M. Matsuo ... [et al.] -- Quantum dot systems. Kondo effect and superconductivity in single InAs quantum dots contacted with superconducting leads / S. Tarucha ... [et al.]. Electron transport

  18. Preface

    Science.gov (United States)

    Batail, Patrick

    2004-04-01

    with p _π-p_π overlap interactions between frontier orbitals of the precursors is today a very active field of research reaching out in field of molecular magnetic materials. Also, the materials chemistry of single component molecular metals and the development of strategies for the chemical control of band filling in molecular metals are areas of intense research. Considerable progress reported in first principle-based electronic structure calculations for large complex systems and band structure calculations of molecular metals should diffuse promptly in the molecular materials community. On the physics side, recent advances in understanding the localization-delocalization-charge ordering competition in low dimensional systems of strongly correlated electrons, and their formulation at ISCOM'03 in a language and format accessible to experimentalists and materials scientists, carries a great many promises for significant developments in the conception of novel molecular superconductors. The physics of one- and two-dimensional molecular metals and superconductors was a strong component of ISCOM'03 with very diverse complementary experimental approaches including transport, uniaxial and isotropie high pressures and high magnetic fields studies, thermal conductivity, STM. Two dimensional conductors have proved to be prototype materials for the study of interacting electron gases through the phenomenon of Mott localization exhibited in some BEDT-TTF salts. Applications of angle-resolved photo-emission investigations have been reported and emerge as a very promising area for future developments. Coupled to quantum chemistry calculations the latter carry along an enormous potential, as exemplified by the wealth of information delivered on the nature of the chemical bonding and electronic structure of molecular solids. The reports of superconductivity induced by a large magnetic field in RETS salts containing magnetic anions have shown how organic materials have brought the