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Sample records for bedt-ttf

  1. Surface-conductive polymer composites based on (BEDT-TTF)2Cu(SCN)2

    International Nuclear Information System (INIS)

    Methods of preparation and studies of the properties of the first polymer composites using (BEDT-TTF)2Cu(SCN)2 (BEDT-TTF=bis(ethylenedithio)tetrathiaf ulvalene) as a conductive phase are reported. It is shown that a network of a conductive (BEDT-TTF)2Cu(SCN)2 salt can be obtained. However, besides superconducting κ-(BEDT-TTF)2Cu(SCN)2 at least two other salts which comprise Cu(SCN)2- are known: α-phase and (BEDT-TTF)Cu2(SCN)3. Scanning electron microscopy (SEM) micrographs and X-ray diffractograms have shown that, although by chemical oxidation the κ-phase is usually obtained, in the composite films the additive crystallization leads mostly to α-(BEDT-TTF)2Cu(SCN)2. (orig.)

  2. 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.

  3. Isotope effect in BEDT-TTF based organic superconductors

    International Nuclear Information System (INIS)

    The results of the comprehensive isotope effect studies, in which seven different isotopically labeled (involving 13C, 34S and 2H labeling) BEDT-TTF derivatives and isotopically labeled anion [Cu(15N13CS)2]- were utilized, are summarized. For the first time, convincing evidence for a genuine BCS-like mass isotope effect in an organic superconductor is revealed in these studies

  4. Bis(vinylenedithio)tetrathiafulvalene analogues of BEDT-TTF.

    Science.gov (United States)

    Ertas, Erdal; Demirtas, İlknur; Ozturk, Turan

    2015-01-01

    This review aims to give an overview of the current status of our research on the synthesis of π-electron donor bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF, ET) analogues prepared from 1,8-diketones via a ring forming reaction. The new synthesized π-electron donors have vinyl moieties producing extended π-electron delocalization over the substituent phenyl rings at the peripheries. PMID:25977714

  5. 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.

  6. Photoluminescence study of the charge transfer salts (BEDT-TTF)2RbHg(SCN)4 and (BEDT-TTF)2KHg(SCN)4

    International Nuclear Information System (INIS)

    We have studied the photoluminescence (PL) spectra of the charge transfer salts (BEDT-TTF)2RbHg(SCN)4 at 1.8 K and (BEDT-TTF)2KHg(SCN)4 in the 1.8-77 K temperature range. Spectra at 1.8 K for both materials display an asymmetric peak at 1.97 eV and a shoulder starting at 1.7 eV. The same features were present in the measured PL spectrum of a neutral-donor BEDT-TTF (ET) molecule crystal, which leads us to associate the peak with a 2 eV intramolecular electronic excitation in the ET and the shoulder with vibronic sidebands. The temperature dependence of the PL spectra of doped and undoped crystals is different, and (ET)2KHg(SCN)4 PL is insensitive to the antiferromagnetic (AFM) phase transition that occurs at 8 K. (orig.)

  7. New results on two synthetic conductors (TMTSF)2BrO4 and (BEDT-TTF)2I3

    DEFF Research Database (Denmark)

    Mortensen, Kell; Jacobsen, C. S.; Bechgaard, K.; Carneiro, K.; Williams, J. M.

    The authors present experimental studies of transport properties of (TMTSF)2BrO4 and (BEDT-TTF)2I3 . The behaviour of the TMTSF salt suggests transport via variable-range hopping among localized states. The BEDT-TTF-salt exhibits thermopower which indicates almost isotropic metallic behaviour in...

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

    International Nuclear Information System (INIS)

    Spin-current injection into an organic semiconductor κ-(BEDT-TTF)2Cu[N(CN)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)2Cu[N(CN)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)2Cu[N(CN)2]Br. We found that the voltage signal in the κ-(BEDT-TTF)2Cu[N(CN)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

  9. 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.

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

    Directory of Open Access Journals (Sweden)

    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.

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

    Directory of Open Access Journals (Sweden)

    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

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

    Directory of Open Access Journals (Sweden)

    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.

  13. 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...

  14. 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

  15. 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.

  16. Simple recipe for formation or recovery at ambient pressure of the 8K superconducting state of β-(BEDT-TTF)2I3

    International Nuclear Information System (INIS)

    A simple recipe for the formation and recovery at ambient pressure of the 8K superconducting state of β-(BEDT-TTF)2I3 is described. This technique will facilitate detailed studies of the 8K state. (author)

  17. 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}.

  18. Fermi-surface topology of κ-(BEDT-TTF)2Cu[N(CN)2]Br at ambient pressure

    International Nuclear Information System (INIS)

    Ambient pressure Fermi-surface measurements are reported for κ-(BEDT-TTF)2Cu[N(CN)2]Br. The single Shubnikov de Haas frequency that is detected (3798±5 T) corresponds to 100% of the Brillouin zone and can be attributed to the β orbit that results from magnetic breakdown. From the temperature dependence of the oscillations, it appears that κ-(BEDT-TTF)2Cu[N(CN)2]Br possesses a conventional Fermi-liquid ground state, although with a short mean free path, possibly due to the presence of Cu(II) ions. The effective mass as determined from the β-orbit oscillations is m*=5.4±0.1me. copyright 1997 The American Physical Society

  19. Spin dynamics and charge order-disorder phase transition detected by EPR in α'-(BEDT-TTF)2IBr2

    OpenAIRE

    Dmitriev, A.; Chernenkaya, A.

    2010-01-01

    Stepwise changes in electron paramagnetic resonance (EPR) parameters (integral intensity, linewidth) accompanying localization of charge carriers have been found in the α'-(BEDT-TTF)2IBr2 crystals. In single crystal exchange narrowing of the EPR lines and sharp decrease in static and dynamic magnetic susceptibility caused by antiferromagnetic interaction of localized charge carriers is observed at Т Т > 50 K a difference between static and dynamic magnetic susceptibility is observed in the...

  20. 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...

  1. Superconductivity of k-(BEDT-TTF) sub 2 Cu[N(CN) sub 2]I under pressure

    CERN Document Server

    Kushch, N D; Yagubskii, E B; Ishiguro, T

    2001-01-01

    The insulating state of k-(BEDT-TTF) sub 2 Cu[N(CN) sub 2]I salt appearing at ambient pressure at low temperatures is suppressed by hydrostatic pressure. The resistive measurement showed that in high-quality crystals the emerging metallic state reveals superconductivity. The superconducting state with the transition temperature of about 8 K is stable at pressures higher than 0.1 GPa

  2. Efficiency Enhancement of Tandem Organic Light-Emitting Devices Fabricated Utilizing an Organic BEDT-TTF and HAT-CN Charge Generation Layer.

    Science.gov (United States)

    Kim, Dae Hun; Kim, Tae Whan

    2015-10-01

    The electrical and optical properties of tandem organic light-emitting devices (OLEDs) fabricated utilizing an organic bis(ethylenedithio)-tetrathiafulvalene (BEDT-TTF) and 1,4,5,8,9,11-hexaazatriphenylenehexacarbonitrile (HAT-CN) charge generation layer (CGL) were investigated to enhance their efficiency. While the operating voltage of the tandem OLEDs with a BEDT-TTF and HAT-CN CGL at 50 mA/cm2 was 11.2 V lower than that of the tandem OLEDs without a CGL, the current efficiency of the tandem OLEDs with a BEDT-TTF and a HAT-CN CGL at 50 mA/cm2 was 0.8 cd/A higher than that of the tandem OLEDs without a CGL. An increase in the current efficiency and a decrease in the operating voltage of the tandem OLEDs with a BEDT-TTF and an HAT-CN CGL were attributed to the enhancement of the electron injection due to its existence in the highest occupied molecular orbital level of the BEDT-TTF between the HAT-CN and the tris-(8-hydroxyquinoline)aluminum layer. PMID:26726464

  3. Coupling of charge and lattice degrees of freedoms in θ-type BEDT-TTF compound probed by low-temperature heat capacity measurements

    Energy Technology Data Exchange (ETDEWEB)

    Yoshimoto, Ryo [Department of Chemistry, Graduate School of Science, Osaka University, Machikaneyama 1-1, Toyonaka, Osaka 560-0043 (Japan); Takane, Yoshiharu [Department of Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology, Ookayama 2-12-1, Meguro-Ku, Tokyo, 152-8551 (Japan); Hino, Kosei; Yamashita, Satoshi [Department of Chemistry, Graduate School of Science, Osaka University, Machikaneyama 1-1, Toyonaka, Osaka 560-0043 (Japan); Nakazawa, Yasuhiro, E-mail: nakazawa@chem.sci.osaka-u.ac.jp [Department of Chemistry, Graduate School of Science, Osaka University, Machikaneyama 1-1, Toyonaka, Osaka 560-0043 (Japan)

    2014-09-15

    Thermodynamic investigations by heat capacity measurements at low temperature between 700 mK and 60 K with magnetic fields up to 8 T for θ-(BEDT-TTF){sub 2}RbZn(SCN){sub 4} and θ-(BEDT-TTF){sub 2}CsZn(SCN){sub 4}, where BEDT-TTF is bisethylenedithiotetrathiafulvalene are performed. In θ-(BEDT-TTF){sub 2}RbZn(SCN){sub 4}, the inter-site Coulomb repulsion produces a charge ordered ground state in the case of slow cooling while a kind of charge cluster glass state appears in rapidly cooled case. The observed finite γ term of 14.8 mJK{sup −2} mol{sup −1} for the rapidly cooled sample demonstrates that the electron density of states remains as metal-like clusters which are localized in the short-range scale. We also discuss the enhancement of the lattice heat capacity and appearance of a kind of Boson peak structure in C{sub p} even in a regular crystal lattice in θ-(BEDT-TTF){sub 2}CsZn(SCN){sub 4.} The low energy phonon modes produced by enhanced charge fluctuations due to the inter-site Coulomb repulsion are the main course of these unusual lattice properties. The features reported here suggest that the coupling of charge degrees of freedom with lattices is important for the systems which do not form rigid charge ordered structures.

  4. Coupling of charge and lattice degrees of freedoms in θ-type BEDT-TTF compound probed by low-temperature heat capacity measurements

    International Nuclear Information System (INIS)

    Thermodynamic investigations by heat capacity measurements at low temperature between 700 mK and 60 K with magnetic fields up to 8 T for θ-(BEDT-TTF)2RbZn(SCN)4 and θ-(BEDT-TTF)2CsZn(SCN)4, where BEDT-TTF is bisethylenedithiotetrathiafulvalene are performed. In θ-(BEDT-TTF)2RbZn(SCN)4, the inter-site Coulomb repulsion produces a charge ordered ground state in the case of slow cooling while a kind of charge cluster glass state appears in rapidly cooled case. The observed finite γ term of 14.8 mJK−2 mol−1 for the rapidly cooled sample demonstrates that the electron density of states remains as metal-like clusters which are localized in the short-range scale. We also discuss the enhancement of the lattice heat capacity and appearance of a kind of Boson peak structure in Cp even in a regular crystal lattice in θ-(BEDT-TTF)2CsZn(SCN)4. The low energy phonon modes produced by enhanced charge fluctuations due to the inter-site Coulomb repulsion are the main course of these unusual lattice properties. The features reported here suggest that the coupling of charge degrees of freedom with lattices is important for the systems which do not form rigid charge ordered structures

  5. Polymorphism and Metallic Behavior in BEDT-TTF Radical Salts with Polycyano Anions

    Directory of Open Access Journals (Sweden)

    Carlos J. Gómez-García

    2012-04-01

    Full Text Available Up to five different crystalline radical salts have been prepared with the organic donor BEDT-TTF and three different polynitrile anions. With the polynitrile dianion tcpd2− (=C[C(CN2]32−, two closely related radical salts: α'-(ET4tcpd·THF (1 (THF = tetrahydrofurane and α'-(ET4tcpd·H2O (2 have been prepared, depending on the solvent used in the synthesis. With the mono-anion tcnoetOH− (=[(NC2CC(OCH2CH2OHC(CN2]− two polymorphs with similar physical properties but different crystal packings have been synthesized: θ-(ET2(tcnoetOH (3 and β''-(ET2(tcnoetOH (4. Finally, with the mono-anion tcnoprOH− (=[(NC2CC(OCH2CH2CH2OHC(CN2]− we have prepared a metallic radical salt: β''-(ET2(tcnoprOH(CH2Cl2CH3Cl0.5 (5. Salts 1‑4 are semiconductors with high room temperature conductivities and activation energies in the range 0.1–0.5 eV, whereas salt 5 is metallic down to 0.4 K although it does not show any superconducting transition above this temperature.

  6. The single-crystal structure of the organic superconductor βCO-(BEDT-TTF)2I3 from a powder grain

    International Nuclear Information System (INIS)

    Synchrotron radiation diffraction data have been collected at 200 K on a microscopic single crystal (dimensions 12 x 10 x 2 μm) of the title compound, where BEDT-TTF is bis(ethylenedithio)tetrathiafulvalene, C10H8S8. The quality of the diffraction data allowed a full structure refinement and enabled the determination of structural details such as the conformations of the ethylene groups as well as the occupancy of the triiodide sites. The compound was found to be slightly iodine-deficient and better described as βCO-(BEDT-TTF)2I3-x [x = 0.014 (3)]. One of the ethylene groups of the BEDT-TTF cation is disordered at this temperature and exists in two distinct conformations with occupancies which are identical within the standard uncertainty. (orig.)

  7. Electric Conductivity of the Zero-gap Semiconducting State in Alpha-(BEDT-TTF)2I3 Salt

    OpenAIRE

    Katayama, Shinya; Kobayashi, Akito; Suzumura, Yoshikazu

    2006-01-01

    The electric conductivity which reveals the zero gap semiconducting (ZGS) state has been investigated as the function of temperature $T$ and life time $\\tau$ in order to understand the ZGS state in quarter-filled $\\alpha$-(BEDT-TTF)$_2$I$_3$ salt with four sites in the unit cell. By treating $\\tau$ as a parameter and making use of the one-loop approximation, it is found that the conductivity is proportional to $T$ and $\\tau$ for $k_B\\gg\\hbar/\\tau$ and independent of $T$ and $\\tau$ for $k_B T\\...

  8. Electrically induced phase transition in α -(BEDT-TTF)2I3 : Indications for Dirac-like hot charge carriers

    Science.gov (United States)

    Peterseim, T.; Ivek, T.; Schweitzer, D.; Dressel, M.

    2016-06-01

    The two-dimensional organic conductor α -(BEDT-TTF)2I3 undergoes a metal-insulator transition at TCO=135 K due to electronic charge ordering. We have conducted time-resolved investigations of its electronic properties in order to explore the field- and temperature-dependent dynamics. At a certain threshold field, the system switches from a low-conducting to a high-conducting state, accompanied by a negative differential resistance. Our time-dependent infrared investigations indicate that close to TCO, the strong electric field pushes the crystal into a metallic state with optical properties similar to the one for T >TCO . Well into the insulating state, however, at T =80 K , the spectral response evidences a completely different electronically induced high-conducting state. Applying a two-state model of hot electrons explains the observations by excitation of charge carriers with a high mobility. They resemble the Dirac-like charge carriers with a linear dispersion of the electronic bands found in α -(BEDT-TTF)2I3 at high pressure. Extensive numerical simulations quantitatively reproduce our experimental findings in all details.

  9. 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.)

  10. Spin dynamics of charge carriers in the process of their localization in α'-(BEDT-TTF)2IBr2 single crystals

    International Nuclear Information System (INIS)

    Sharp changes in the integral intensity and linewidth of the ESR spectrum that accompany the localization of the charge carriers have been revealed in α'-(BEDT-TTF)2IBr2 crystals. It has been found that the types of localization in two compounds under investigation are different: charge carriers in β''-(BEDT-TTF)4NH4[Cr(C2O4)3] are localized on irregular defects of the crystal lattice, whereas charge carriers in α'-(BEDT-TTF)2IBr2 are localized at the regular positions of the unit cell. The exchange narrowing of the ESR line and a sharp decrease in the dc and ac magnetic susceptibilities are observed in α'-(BEDT-TTF)2IBr2 at low temperatures T 2IBr2 at high temperatures T > 50 K differ from each other, because the thermally activated hopping frequency of the charge carriers is higher than the frequency of the measuring UHF field of an ESR spectrometer.

  11. 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.

  12. Studies of the microwave resistivity of κ-(BEDT-TTF)2Cu[N(CN)2]Cl

    International Nuclear Information System (INIS)

    The authors have performed temperature dependent measurements of the surface impedance of κ-(BEDT-TTF)2Cu[N(CN)2]Cl in both directions, parallel and perpendicular to the highly conducting planes. In both orientations the microwave resistivity basically follows the dc behavior for T > 15 K: the crystal undergoes a broad metal-insulator transition at around 50 K. While there are no indications of superconductivity at ambient pressure found in the dc resistivity and by ac susceptibility, the microwave resistivity clearly drops at 13 K and again at 5 K, indicating two superconducting phases. When pressure is applied by embedding it in grease, only the well known superconducting phase transition at Tc = 13 K remains

  13. Anisotropic magnetoresistance in the organic superconductor βdouble-prime-(BEDT-TTF)2SF5CH2CF2SO3

    International Nuclear Information System (INIS)

    In this paper, we report transport measurements of interlayer magnetoresistance with field parallel and perpendicular to the current direction in an all organic superconductor βdouble-prime-(BEDT-TTF)2SF5CH2CF2SO3. For H parallel I, the isothermal magnetoresistance R(H) at low temperatures (T≤Tc) displays a peak effect as a function of field. For H perpendicular I, R(H) increases monotonically with increasing field. The results are very analogous to the interlayer magnetoresistance in κ-(BEDT-TTF)2X compounds. The observation of the peak effect or negative magnetoresistance in different systems for H parallel I perpendicular plane suggests that it is intrinsic to the layered organic superconductors. For H perpendicular I, the large positive magnetoresistance is in a general agreement with a two band model for charge transport. copyright 1999 The American Physical Society

  14. Anomalous damping effects of magneto-quantum oscillations in the extremely 2D electronic system κ-(BEDT-TTF)2I3

    International Nuclear Information System (INIS)

    The electronic system of the organic superconductor κ-(BEDT-TTF)2I3 (BEDT-TTF=bis(ethylenedithiolo)tetrathi afulvalene) is identified as extremely two-dimensional (2D). The topology of the Fermi surface (FS) was investigated by means of Shubnikov-de Haas (SdH) as well as de Haas-van Alphen (dHvA) experiments focusing on the verification of the 2D character of the system. This two-dimensionality specially takes effect as soon as the magnetic field is oriented exactly perpendicular to the conducting planes (i.e. Θ=0 ). Under such conditions strong anomalous damping effects in the field and temperature dependence of quantum oscillation amplitudes are observed. These anomalous damping effects are discussed in terms of the occurrence of quasi-particle excitations with fractional statistics (QPFS) which may only occur in extremely 2D systems at high magnetic fields and low temperatures (i.e., only when ℎωC>>kBT). Taking up these requirements, the aim of this work is to quantify the extreme two-dimensionality of the electronic system of κ-(BEDT-TTF)2I3 and to show that the observed damping effects in fact are determined by the ratio ℎωC/kBT. These facts may support the interpretation of the observed damping effects of quantum oscillation amplitudes at high magnetic fields, low temperatures and Θ=0 as generated by the possible occurrence of such QPFS. (orig.)

  15. 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

  16. Electronic properties close to Dirac cone in two-dimensional organic conductor α-(BEDT-TTF)2I3

    Science.gov (United States)

    Katayama, S.; Kobayashi, A.; Suzumura, Y.

    2009-01-01

    A zero-gap state (ZGS) has been found in a bulk system of two-dimensional organic conductor, α-(BEDT-TTF)2I3 salt which consists of four sites of donor molecules in a unit cell. In the present paper, the characteristic of the ZGS is analyzed in detail and the electronic properties are examined in the vicinity of the Dirac point where the conduction and valence bands degenerate to form the zero-gap. The eigenvectors of the energy band have four components of respective sites, where two of them correspond to inequivalent sites and the other two correspond to equivalent sites. It is shown that the former exhibits an exotic momentum dependence around the contact point and the latter shows almost a constant dependence. The density of states of each site close to the Dirac point is calculated to demonstrate the temperature dependence of the local magnetic susceptibility and the local nuclear magnetic relaxation rate. Further, the robust property of the ZGS against the anion potential is also shown by using the second-order perturbation.

  17. 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

  18. 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.

  19. Investigation of Vortex Behavior in the Organic Superconductor κ-(BEDT-TTF)2Cu(SCN)2 Using Muon Spin Rotation

    International Nuclear Information System (INIS)

    Muon spin rotation (μSR) measurements have been performed on the organic superconductor κ-(BEDT-TTF)2Cu(SCN)2 in order to investigate its exotic vortex behavior. Previously unobserved features of the μSR line shapes have been measured at low fields and temperatures. In the mixed state the existence of a lattice composed of linear vortices is demonstrated at low fields. The breakup of this well-ordered lattice has furthermore been observed as a function of both field and temperature. copyright 1997 The American Physical Society

  20. 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 ...

  1. 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). PMID:26076168

  2. Role of layer packing for the electronic properties of the organic superconductor (BEDT-TTF)$_2$Ag(CF$_3$)$_4$(TCE)

    OpenAIRE

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

    2015-01-01

    The charge transfer compound (BEDT-TTF)$_2$Ag(CF$_3$)$_4$(TCE) crystallizes in three polymorphs with different alternating layers: While a phase with a $\\kappa$ packing motif has a low superconducting transition temperature of $T_c=2.6$ K, two phases with higher $T_c$ of $9.5$ and $11$ K are multi-layered structures consisting of $\\alpha'$ and $\\kappa$ layers. We investigate these three systems within density functional theory and find that the $\\alpha'$ layer shows different degrees of charg...

  3. 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.

  4. Anomalous behaviour of the in-plane electrical conductivity of the layered superconductor κ-(BEDT-TTF)2Cu(NCS)2

    International Nuclear Information System (INIS)

    The apparent quasiparticle scattering rates in high-quality crystals of the quasi-two-dimensional superconductor κ-(BEDT-TTF)2Cu(NCS)2 are studied using the Shubnikov-de Haas effect and megahertz penetration-depth experiments. The width of the superconducting transition observed in the megahertz experiments, taken in conjunction with the field dependence of the Shubnikov-de Haas oscillations, gives evidence that the broadening of the Landau levels is primarily caused by spatial inhomogeneities. This indicates a quasiparticle lifetime for the Landau states >> 3 ps. The megahertz data can also be used to derive an apparent scattering time (0.14- 0.56 ps) from the skin depth. This is much shorter than the Landau-state lifetime, in strong contrast to the expectations of Landau Fermi-liquid theory. The simplest explanation for the data is that only a fraction of the crystal contributes to the metallic conductivity, an observation which may be related to the recently observed 'glassy' transition in κ-(BEDT-TTF)2Cu(NCS)2. (letter to the editor)

  5. 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.

  6. Magnetoresistance peak in the mixed state of the organic superconductor κ-(BEDT-TTF)2Cu[N(CN)2]Br

    International Nuclear Information System (INIS)

    In this letter, the authors report transport measurements with field and current parallel to the b axis (perpendicular to the conducting plane) in the organic superconductor κ-(BEDT-TTF)2Cu[N(CN)2]Br. The isothermal magnetoresistance R(H) displays a peak effect as a function of field. The peak resistance is substantially larger than that in large fields. The results are in sharp contrast to the conventional dissipation mechanisms in the mixed state of anisotropic superconductors, as in the case of Bi2Sr2CaCu2O8. Comparison with Hc2(T) obtained from magnetic measurements shows that the peak effect in R(H) occurs in the mixed state. Analysis of the data suggests a much larger Josephson junction resistance in the mixed state than that in the normal state, indicative of a new charge transport scattering mechanism in the presence of vortices

  7. 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.

  8. Thermal expansion studies on low-dimensional frustrated quantum magnets. The case of κ-(BEDT-TTF)2Cu2(CN)3 and azurite

    International Nuclear Information System (INIS)

    Thermal expansion measurements provide a sensitive tool for exploring a material's thermodynamic properties in condensed matter physics as they provide useful information on the electronic, magnetic and lattice properties of a material. In this thesis, thermal expansion measurements have been carried out both at ambient-pressure and under hydrostatic pressure conditions. From the materials point of view, the spin-liquid candidate κ-(BEDT-TTF)2Cu2(CN)3 has been studied extensively as a function of temperature and magnetic field. Azurite, Cu3(CO3)2(OH)2 - a realization of a one-dimensional distorted Heisenberg chain is also studied both at ambient and hydrostatic pressure to demonstrate the proper functioning of the newly built setup ''thermal expansion under pressure''.

  9. Non-fermi liquid behavior of the organic superconductor κ-(BEDT-TTF)4Hg2.89Br8 probed by 13C-NMR

    International Nuclear Information System (INIS)

    We assessed 13C-NMR measurements in an organic salt, κ-(BEDT-TTF)4Hg2.89Br8, which exhibits superconductivity at 4.3 K under ambient pressure. We observed that (T1T)-1 of H|| and -perpendicular layer at ambient pressure increased as the temperature was decreased to 7 K, but decreased further at lower temperatures, suggesting that the decrease of (T1T)-1 was not due to the superconductive fluctuations, but due to the magnetism of the conduction electrons. Application of pressure suppresses (T1T)-1, with (T1T)-1 becoming constant above 2 GPa. These results suggest that applying pressure alters the electron system from a non-Fermi liquid (NFL) to a Fermi liquid (FL) state and that antiferromagnetic fluctuations contribute to the origin of NFL behavior. Whereas most organic conductors show Fermi liquid behavior, this salt is an organic superconductor that shows NFL behavior due to the antiferromagnetic fluctuations.

  10. 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.

  11. Magnetic quantum oscillations in the charge-density-wave state of the organic metals a-(BEDT-TTF)2MHg(SCN)4 with M = K and Tl

    International Nuclear Information System (INIS)

    The low-temperature charge-density-wave (CDW) state in the layered organic metals α-(BEDT-TTF)2MHg(SCN)4 has been studied by means of the Shubnikov-de Haas and de Haas-van Alphen effects. In addition to the dominant α-frequency, which is also observed in the normal state, both the magnetoresistance and magnetic torque possess a slowly oscillating component. These slow oscillations provide a firm evidence for the CDW-induced reconstruction of the original cylindrical Fermi surface. The α-oscillations of the interlayer magnetoresistance exhibit an anoma-lous phase inversion in the CDW state, whereas the de Haas-van Alphen signal maintains the normal phase. We argue that the anomaly may be attributed to the magnetic-breakdown origin of the α-oscillations in the CDW state. A theoretical model illustrating the possibility of a phase inversion in the oscillating interlayer conductivity in the presence of a spatially fluctuating magnetic breakdown gap is proposed

  12. Anomalous behaviour of the in-plane electrical conductivity of the layered superconductor kappa-(BEDT-TTF) sub 2 Cu(NCS) sub 2

    CERN Document Server

    Singleton, J; Hayes, W; Schlüter, J A

    2003-01-01

    The apparent quasiparticle scattering rates in high-quality crystals of the quasi-two-dimensional superconductor kappa-(BEDT-TTF) sub 2 Cu(NCS) sub 2 are studied using the Shubnikov-de Haas effect and megahertz penetration-depth experiments. The width of the superconducting transition observed in the megahertz experiments, taken in conjunction with the field dependence of the Shubnikov-de Haas oscillations, gives evidence that the broadening of the Landau levels is primarily caused by spatial inhomogeneities. This indicates a quasiparticle lifetime for the Landau states >> 3 ps. The megahertz data can also be used to derive an apparent scattering time (0.14- 0.56 ps) from the skin depth. This is much shorter than the Landau-state lifetime, in strong contrast to the expectations of Landau Fermi-liquid theory. The simplest explanation for the data is that only a fraction of the crystal contributes to the metallic conductivity, an observation which may be related to the recently observed 'glassy' transition in k...

  13. 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.

  14. Cyclotron resonance and De Haas-Van Alphen effect in (BEDT-TTF) sub 8 Hg sub 4 Cl sub 1 sub 2 (C sub 6 H sub 5 Cl) sub 2 organic conductor

    CERN Document Server

    Voskobojnikov, I B; Samarin, N A; Cluchanko, N E; Lyubovskaya, R N; Moshchalkov, V V

    2002-01-01

    Within 0.33-1.44 K temperature range at B <= 50 T magnetic field values one measured the De Haas-Van Alphen effect for (BEDT-TTF) sub 8 Hg sub 4 Cl sub 1 sub 2 (C sub 6 H sub 5 Cl) sub 2 organic quasi-two-dimensional conductor. Analysis of quantum oscillations with regard to data on cyclotron resonance derived for 40-120 GHz frequency interval enabled to determine that a complex spectrum of quantum oscillations was formed by alpha approx 256 T and beta approx 670-610 T fundamental frequencies as well as, by combination and multiple frequencies. It is shown that nature of temperature rearrangement of oscillation spectrum may be interpreted in terms of model taking account of occurrence of magnetic phase transition at T sub c approx 0.9 K and proximity of a fundamental frequency with m* = 1.48m sub 0 efficient mass to the spin dumping condition

  15. 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.

  16. Fermi surface studies of low-dimensional organic conductors based on BEDT-TTF

    Energy Technology Data Exchange (ETDEWEB)

    Singleton, John [Department of Physics, University of Oxford, The Clarendon Laboratory, Parks Road, Oxford OX1 3PU (United Kingdom); Caulfield, Jason [Department of Physics, University of Oxford, The Clarendon Laboratory, Parks Road, Oxford OX1 3PU (United Kingdom); Hill, Stephen [Department of Physics, University of Oxford, The Clarendon Laboratory, Parks Road, Oxford OX1 3PU (United Kingdom); Blundell, Stephen [Department of Physics, University of Oxford, The Clarendon Laboratory, Parks Road, Oxford OX1 3PU (United Kingdom); Lubczynski, Wieslaw [Department of Physics, University of Oxford, The Clarendon Laboratory, Parks Road, Oxford OX1 3PU (United Kingdom); House, Andrew [Department of Physics, University of Oxford, The Clarendon Laboratory, Parks Road, Oxford OX1 3PU (United Kingdom); Hayes, William [Department of Physics, University of Oxford, The Clarendon Laboratory, Parks Road, Oxford OX1 3PU (United Kingdom); Perenboom, Jos [High Field Magnet Laboratory and Research Institute for Materials, NL 6525 ED Nijmegen (Netherlands); Kurmoo, Mohammedally [The Royal Institution, 21 Albemarle Street, London W1X 4BS (United Kingdom); Day, Peter [The Royal Institution, 21 Albemarle Street, London W1X 4BS (United Kingdom)

    1995-05-01

    This paper provides an introduction to charge-transfer salts of the ion bis(ethylenedithio)tetrathiafulvalene (ET) and their band-structure, and reviews some recent experiments on the salts involving high magnetic fields carried out by the Oxford group and coworkers. (orig.).

  17. Fermi surface studies of low-dimensional organic conductors based on BEDT-TTF

    International Nuclear Information System (INIS)

    This paper provides an introduction to charge-transfer salts of the ion bis(ethylenedithio)tetrathiafulvalene (ET) and their band-structure, and reviews some recent experiments on the salts involving high magnetic fields carried out by the Oxford group and coworkers. (orig.)

  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. Magnetothermopower in unconventional density waves

    International Nuclear Information System (INIS)

    After a brief introduction on unconventional density waves (i.e. unconventional charge density wave (UCDW) and unconventional spin density wave (USDW)), we discuss the magnetotransport of the low temperature phase (LTP) of α-(BEDT-TTF)2KHg(SCN)4. Recently we have proposed that the low temperature phase in α-(BEDT-TTF)2KHg(SCN4 should be UCDW. Here we show that UCDW describes very consistently the magnetothermopower of )α-(BEDT-TTF)2KHg(SCN)4 observed by Choi et al. (author)

  3. 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...

  4. Enhanced T{sub c} in a dual-layered molecular superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Souza, Mariano de; Lang, Michael [Physikalisches Institut, J.W. Goethe-Universitaet, SFB/TR49, D-60438 Frankfurt/M (Germany); Wiehl, Leonor [Institut fuer Geowissenschaften, J.W. Goethe-Universitaet, D-60438 Frankfurt/M (Germany); Schlueter, John A. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

    2011-07-01

    We have revisited the structural and electronic properties of the filamentary organic superconductor (BEDT-TTF){sub 2}Ag(CF{sub 3}){sub 4}(TCE), first synthesized in 1994. Detailed structural investigations reveal that the BEDT-TTF molecules are arranged in two distinctly different packing motifs, {kappa} and {alpha}', which alternate from layer to layer. This molecule-based superconductor with dual BEDT-TTF packing motifs has a T{sub c} five times higher than that of its polymorph that contains only {kappa}-type packing. Using the established empirical correlations between the bond lengths (C-S and C=S) and the oxidation state of the BEDT-TTF molecule, we have found that there is a uniform charge distribution in the {kappa}-layers (corresponding to an oxidation state of +0.5 for all BEDT-TTF molecules), whereas in the {alpha}'-layer, half of the molecules are nearly fully oxidized to +1, while the other half are close to neutral, resulting in a charge-ordered neutral layer. These findings indicate that this material can be considered as a promising candidate for a distinctly two-dimensional superconductor.

  5. Enhanced Tc in a dual-layered molecular superconductor

    International Nuclear Information System (INIS)

    We have revisited the structural and electronic properties of the filamentary organic superconductor (BEDT-TTF)2Ag(CF3)4(TCE), first synthesized in 1994. Detailed structural investigations reveal that the BEDT-TTF molecules are arranged in two distinctly different packing motifs, κ and α', which alternate from layer to layer. This molecule-based superconductor with dual BEDT-TTF packing motifs has a Tc five times higher than that of its polymorph that contains only κ-type packing. Using the established empirical correlations between the bond lengths (C-S and C=S) and the oxidation state of the BEDT-TTF molecule, we have found that there is a uniform charge distribution in the κ-layers (corresponding to an oxidation state of +0.5 for all BEDT-TTF molecules), whereas in the α'-layer, half of the molecules are nearly fully oxidized to +1, while the other half are close to neutral, resulting in a charge-ordered neutral layer. These findings indicate that this material can be considered as a promising candidate for a distinctly two-dimensional superconductor.

  6. Mixed-stack organic charge-transfer complexes with intercolumnar networks

    International Nuclear Information System (INIS)

    We report synthesis and examination of the electronic properties of an isomorphous series of mixed-stack organic charge-transfer complexes, composed of [bis(ethylenedithio)tetrathiafulvalene] (BEDT-TTF)-based electron donors and electron acceptors of halogen-substituted tetracyanoquinodimethanes (TCNQ's). Single crystals of (BEDT-TTF)(Me2TCNQ), (BEDT-TTF)(ClMeTCNQ), and (BEDO-TTF)(Cl2TCNQ) were investigated as to their crystal structures, and optical and magnetic properties. The intermolecular overlaps between the stacked columns were comparable to the face-to-face overlap between the donor and the acceptor molecules inside the stacks. As seen from the optical and magnetic measurements, the (BEDT-TTF)(Me2TCNQ) and (BEDT-TTF)(ClMeTCNQ) complexes were neutral, while the (BEDO-TTF)(Cl2TCNQ) complex was found to be ionic. Among these complexes, anomalous magnetic properties were observed in the ionic complex of (BEDO-TTF)(Cl2TCNQ). (BEDO-TTF)(Cl2TCNQ) is a magnetic insulator with Curie-Weiss behavior in magnetic susceptibility followed by a sharp drop at around 120 K, which is in sharp contrast to conventional 'spin-Peierls-type' nonmagnetic mixed-stack ionic compounds

  7. 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 (Del) 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 has been applied to study the interplay of superconductivity and ferromagnetism for (BEDT-TTF)213 system. These results reveal that superconductivity and SDW state coexist in k-(BEDT-TTF)213 salt with a layered crystal structure. (author)

  8. 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)

  9. 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

  10. 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.

  11. 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.

  12. Optical studies of crystalline organic superconductors under extreme conditions

    CERN Document Server

    McDonald, R D

    2001-01-01

    the aim being to make an optical measurement of the pressure dependence of the charge carrier effective mass. Chapter 4 concentrates on the vibrational modes of kappa-(BEDT-TTF) sub 2 Cu(SCN) sub 2. This chapter reports the first Raman scattering experiments on an organic superconductor at high pressure. Comparison of the infrared reflectance and Raman scattering measurements are used to elucidate the role of electron-phonon coupling in this material's superconductivity. Chapter 5 reports the first non-resonant measurements of the GHz conductivity of an organic molecular superconductor. These experiments probe the unconventional metallic properties of an organic superconductor during the onset of superconductivity. This thesis reports experiments which involve the interaction of light and matter to probe the properties of crystalline organic superconductors. The organic superconductors of the BEDT-TTF family are prototypical correlated electron systems; their low-temperature ground states are dominated by man...

  13. Aspects of unconventional density waves

    International Nuclear Information System (INIS)

    Recently many people discuss unconventional density waves (i.e. unconventional charge density waves (UCDW) and unconventional spin density waves (USDW)). Unlike in conventional density waves, the quasiparticle spectrum in these systems is gapless. Also these systems remain metallic. Indeed it appears that there are many candidates for UDW. The low temperature phase of α-(BEDT-TTF)2KHg(SCN)4, the antiferromagnetic phase in URu2Si2, the CDW in transition metal dichalcogenite NbSe2, the pseudogap phase in high Tc cuprate superconductors, the glassy phase in organic superconductor κ-(BEDT-TTF)2Cu[N(CN)2]Br. After a brief introduction on UCDW and USDW, we shall discuss some of the above systems, where we believe we have evidence for unconventional density waves. (author)

  14. Optical studies of crystalline organic superconductors under extreme conditions

    International Nuclear Information System (INIS)

    This thesis reports experiments which involve the interaction of light and matter to probe the properties of crystalline organic superconductors. The organic superconductors of the BEDT-TTF family are prototypical correlated electron systems; their low-temperature ground states are dominated by many-body interactions and their infrared spectra contain contributions typical of an interacting Fermi liquid: single particle excitations, collective modes and multiparticle excitations. Optical measurements hence provide a unique tool for probing these phenomena. Extreme environments, such as low temperature and high hydrostatic pressure, are used to tune the various interaction strengths, providing a link to the superconducting properties. For example, the superconducting transition temperature in κ-(BEDT- TTF)2Cu(SCN)2 falls from 10 K at ambient pressure to 0 at 0.5 GPa. This thesis presents systematic attempts to identify the many-body interactions responsible for superconductivity on these materials. Chapter 1 introduces the samples under investigation and reviews the relevant background theory pertaining to the interaction of light and matter. Chapter 2 discusses experimental techniques, specifically techniques for carrying out infrared and Raman scattering experiments at high pressure and low temperature. Chapter 3 reports the results of the first high-pressure infrared measurement on an organic superconductor, namely κ-(BEDT-TTF)2Cu(SCN)2, the aim being to make an optical measurement of the pressure dependence of the charge carrier effective mass. Chapter 4 concentrates on the vibrational modes of κ-(BEDT-TTF)2Cu(SCN)2. This chapter reports the first Raman scattering experiments on an organic superconductor at high pressure. Comparison of the infrared reflectance and Raman scattering measurements are used to elucidate the role of electron-phonon coupling in this material's superconductivity. Chapter 5 reports the first non-resonant measurements of the GHz

  15. Scanning tunneling microscopy of silver containing salt of bis(ethylenedithio)tetrathiafulvalene

    OpenAIRE

    Bai, C.; Dai, C.; Zhu, C. (Changbin); Z. Chen; G Huang; Wu, X; Zhu, D.; Baldeschwieler, John D.

    1990-01-01

    The surface of silver containing salt of bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) was studied with the computer-controlled scanning tunneling microscope developed in our laboratory. The crystal surface of the charge-transfer complex is well ordered and a regular array of corrugations is clearly visible. The prominent feature of the experimental scanning tunneling microscopy images is in agreement with the bulk crystal structure obtained by x-ray diffraction method.

  16. 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 ...

  17. Experimental evidence for Froehlich superconductivity in high magnetic fields

    International Nuclear Information System (INIS)

    Resistivity and irreversible magnetization data taken within the high magnetic field CDWx phase of the quasi-two-dimensional organic metal α-(BEDT-TTF)2KHg(SCN)4 are shown to be consistent with a field-induced inhomogeneous superconducting phase. In-plane skin depth measurements show that the resistive transition on entering the CDWx phase is both isotropic and representative of the bulk. (author). Letter-to-the-editor

  18. 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...

  19. 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.

  20. Magneto-optical studies of low-dimensional organic conductors

    Directory of Open Access Journals (Sweden)

    Hitoshi Ohta, Motoi Kimata and Yugo Oshima

    2009-01-01

    Full Text Available Our periodic orbit resonance (POR results on quasi-two-dimensional (q2D, highly anisotropic q2D and quasi-one-dimensional (q1D organic conductors are reviewed together with our rotational cavity magneto-optical measurement system. Higher order POR up to seventh order has been observed in the q2D system (BEDT-TTF2Br(DIA, and the experimental conditions to observe POR and the cyclotron resonance (CR are discussed. Highly anisotropic q2D Fermi surface (FS in β''-(BEDT-TTF(TCNQ, which was considered to have q1D FS previously, is proposed by our POR measurements, and the possible interpretations of other experimental results of β''-(BEDT-TTF(TCNQ are discussed assuming the highly anisotropic q2D FS. Finally, detailed q1D FS of (DMET2I3, obtained from our POR results, is discussed in connection with the typical q1D system (TMTSF2ClO4.

  1. 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.

  2. Transport Properties of a spinon Fermi surface coupled to a U(1) gauge field

    OpenAIRE

    Nave, Cody P.; Lee, Patrick A.

    2007-01-01

    With the organic compound $\\kappa$-(BEDT-TTF)$_2$-Cu$_2$(CN)$_3$ in mind, we consider a spin liquid system where a spinon Fermi surface is coupled to a U(1) gauge field. Using the non-equilibrium Green's function formalism, we derive the Quantum Boltzmann Equation (QBE) for this system. In this system, however, one cannot a priori assume the existence of Landau quasiparticles. We show that even without this assumption one can still derive a linearized equation for a generalized distribution f...

  3. Charge ordering in low dimensional organic conductors: Structural aspects

    Energy Technology Data Exchange (ETDEWEB)

    Pouget, Jean-Paul; Foury-Leylekian, Pascale [Laboratoire de Physique des Solides, Universite Paris-sud, CNRS UMR 8502, Batiment 510, 91405 Orsay Cedex (France); Alemany, Pere [Departament de Quimica Fisica and Institut de Quimica Teorica i Computacional (IQTCUB), Universitat de Barcelona, Diagonal 627, 08028 Barcelona (Spain); Canadell, Enric [Institut de Ciencia de Materials de Barcelona, CSIC, Campus UAB, 08193 Bellaterra (Spain)

    2012-05-15

    The paper points out the importance of the coupling between anions and donors in order to achieve the 4k{sub F} charge localization observed in (TMTTF){sub 2}PF{sub 6}, {delta}-(EDT-TTF-CONMe{sub 2}){sub 2}Br and (o-DMTTF){sub 2}Cl/Br salts, the 2k{sub F} charge density wave (CDW) ground state of {alpha}-(BEDT-TTF){sub 2}KHg(SCN){sub 4} and the metal to insulator transition of {alpha}-(BEDT-TTF){sub 2}I{sub 3}. This coupling leads to a cooperative displacement wave of the anions accompanied by a modulation of the density of {pi} holes on the donors. We distinguish two principal anion-donor coupling mechanisms: a direct mechanism via the Hartree anion potential on donor sites and an indirect mechanism via the polarization of {sigma} bonds activated by the modification of the H bonds network. Both kinds of interaction are tuned by the relative displacement of the anions with respect to the donors. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  4. Superconducting properties and Fermi-surface topology of the quasi-two-dimensional organic superconductor λ-(BETS)2GaCl4 (BETS≡bis(ethylene-dithio)tetraselenafulvalene)

    International Nuclear Information System (INIS)

    The Fermi-surface topology of the organic superconductor λ-(BETS)2GaCl4 has been determined using the Shubnikov-de Haas and magnetic breakdown effects and angle-dependent magnetoresistance oscillations. The former experiments were carried out in pulsed fields of up to 60 T, whereas the latter employed quasistatic fields of up to 30 T. All of these data show that the Fermi-surface topology of λ-(BETS)2GaCl4 is very similar to that of the most heavily studied organic superconductor, κ-(BEDT-TTF)2Cu(NCS)2 (BEDT-TTF≡bis(ethylene-dithio)tetrathiafulvalene), except in one important respect: the interplane transfer integral of λ-(BETS)2GaCl4 is a factor ∼5 larger than that of κ-(BEDT-TTF)2Cu(NCS)2. The increased three-dimensionality of λ-(BETS)2GaCl4 is manifested in radio-frequency penetration-depth measurements, which show a clear dimensional crossover in the behaviour of Hc2(T). The radio-frequency measurements have also been used to extract the Labusch parameter determining the fluxoid interactions as a function of temperature, and to map the flux-lattice melting curve. (author)

  5. 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.

  6. 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...

  7. Exotic Quantum Phases and Phase Transitions of Strongly Interacting Electrons in Low-Dimensional Systems

    Science.gov (United States)

    Mishmash, Ryan V.

    Experiments on strongly correlated quasi-two-dimensional electronic materials---for example, the high-temperature cuprate superconductors and the putative quantum spin liquids kappa-(BEDT-TTF)2Cu2(CN)3 and EtMe3Sb[Pd(dmit)2]2---routinely reveal highly mysterious quantum behavior which cannot be explained in terms of weakly interacting degrees of freedom. Theoretical progress thus requires the introduction of completely new concepts and machinery beyond the traditional framework of the band theory of solids and its interacting counterpart, Landau's Fermi liquid theory. In full two dimensions, controlled and reliable analytical approaches to such problems are severely lacking, as are numerical simulations of even the simplest of model Hamiltonians due to the infamous fermionic sign problem. Here, we attempt to circumvent some of these difficulties by studying analogous problems in quasi-one dimension. In this lower dimensional setting, theoretical and numerical tractability are on much stronger footing due to the methods of bosonization and the density matrix renormalization group, respectively. Using these techniques, we attack two problems: (1) the Mott transition between a Fermi liquid metal and a quantum spin liquid as potentially directly relevant to the organic compounds kappa-(BEDT-TTF)2Cu 2(CN)3 and EtMe3Sb[Pd(dmit)2] 2 and (2) non-Fermi liquid metals as strongly motivated by the strange metal phase observed in the cuprates. In both cases, we are able to realize highly exotic quantum phases as ground states of reasonable microscopic models. This lends strong credence to respective underlying slave-particle descriptions of the low-energy physics, which are inherently strongly interacting and also unconventional in comparison to weakly interacting alternatives. Finally, working in two dimensions directly, we propose a new slave-particle theory which explains in a universal way many of the intriguing experimental results of the triangular lattice organic spin

  8. 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

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. Brave new world of unconventional density waves

    International Nuclear Information System (INIS)

    Recently many people have discussed unconventional density wave (i.e. UCDW and USDW). Unlike in conventional density waves, the quasiparticle excitations in these systems are gapless. The appearance of these systems suggests paradigm shift from quasi 1D system to quasi 2D and 3D systems. Here we limit ourselves to the angular dependent magnetoresistance (ADMR) observed in the low temperature phase (LTP) of α-(BEDT-TTF)2KHg(SCN)4. Here we show that UCDW describes successfully many features of ADMR as manifestation of the Landau quantization of the quasiparticle spectrum in magnetic field. Indeed ADMR will provide a unique window to access UDW like the AF phase in URu2Si2, the pseudogap phase in high Tc cuprates and the glassy phase in organic superconductor k-(ET)2 salts. (author)

  14. 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}.

  15. 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.

  16. Angle-dependent vortex structure in a high anisotropy superconductor

    International Nuclear Information System (INIS)

    Angle-dependent muon spin rotation measurements have been made on the organic superconductor κ-(BEDT-TTF)2Cu(SCN)2. Oscillations are observed in the width of the internal field distribution, which are periodic in the perpendicular component of the applied magnetic field, Bz=B cos θ, with a uniform period over a range of angles and fields. These oscillations are superimposed on the standard cos θ scaling expected for the width in a highly anisotropic superconductor. The oscillation period is of order 2 mT and the amplitude is particularly strong at fields comparable with the period. The origin of this novel phenomenon is discussed in terms of the low field instabilities of tilted vortices in this highly anisotropic superconductor

  17. Development of an optical time-resolved measurement system under high-pressure and low-temperature with a piston-cylinder pressure cell

    Science.gov (United States)

    Tsuchiya, Satoshi; Kino, Yohei; Nakagawa, Koichi; Nakagawa, Daisuke; Yamada, Jun-ichi; Toda, Yasunori

    2016-04-01

    To perform the femtosecond pump-probe spectroscopy under high pressure and low temperature, we constructed a measurement system with a piston cylinder type pressure cell installing an optical fiber bundle. The applied pressure was achieved to 6 kbar and the cell was cooled down to 15 K. Several demonstrations revealed that broadening and change of polarization of pulse (duration of ˜120 fs) owing to the dispersions in the fiber bundle are much small indicating that those have little influence on the measurement of carrier relaxation dynamics. In the measurements of κ-(BEDT-TTF)2Cu(NCS)2 under 1.3 kbar at 43 K, we have successfully detected the polarization anisotropy of the carrier relaxation dynamics and estimated the decay time in the same way as the normal measurement.

  18. 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

  19. 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.)

  20. Coexistence of ferromagnetism and metallic conductivity in a molecule-based layered compound.

    Science.gov (United States)

    Coronado, E; Galán-Mascarós, J R; Gómez-García, C J; Laukhin, V

    2000-11-23

    Crystal engineering--the planning and construction of crystalline supramolecular architectures from modular building blocks--permits the rational design of functional molecular materials that exhibit technologically useful behaviour such as conductivity and superconductivity, ferromagnetism and nonlinear optical properties. Because the presence of two cooperative properties in the same crystal lattice might result in new physical phenomena and novel applications, a particularly attractive goal is the design of molecular materials with two properties that are difficult or impossible to combine in a conventional inorganic solid with a continuous lattice. A promising strategy for creating this type of 'bi-functionality' targets hybrid organic/inorganic crystals comprising two functional sub-lattices exhibiting distinct properties. In this way, the organic pi-electron donor bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) and its derivatives, which form the basis of most known molecular conductors and superconductors, have been combined with molecular magnetic anions, yielding predominantly materials with conventional semiconducting or conducting properties, but also systems that are both superconducting and paramagnetic. But interesting bulk magnetic properties fail to develop, owing to the discrete nature of the inorganic anions. Another strategy for achieving cooperative magnetism involves insertion of functional bulky cations into a polymeric magnetic anion, such as the bimetallic oxalato complex [MnIICrIII(C2O4)3]-, but only insoluble powders have been obtained in most cases. Here we report the synthesis of single crystals formed by infinite sheets of this magnetic coordination polymer interleaved with layers of conducting BEDT-TTF cations, and show that this molecule-based compound displays ferromagnetism and metallic conductivity. PMID:11100721

  1. 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

  2. Conductors with small Fermi energies and small gap energies

    International Nuclear Information System (INIS)

    If the Fermi energy is of the order of meV's, the usual treatment of the density of free electrons is not valid, but use can be made of an averaged density of states that depends weakly on temperature, so that the temperature variation of the conductivity can be expressed by the equation: σ congruent CT(1-s) 1n{[(exp(βEf) + 1)/2][exp(-β(Eg - Ef)) + 1)]} in which Ef is the Fermi energy, Eg is the top of the energy gap for thermal activation, s is the exponent of the temperature-dependent scattering. This equation serves to define a class of solids consisting of a microcomposite with a narrow conduction band for which Ef of the order of ceV's or less and a thermal activated conduction for which Eg is of the order of ceV's. It describes quantitatively the conductivity, σ(T;Δ, for YBa2Cu3O7-Δ and σ(T;p) as the hydrostatic pressure p is varied for κ-(BEDT-TTF)2CuN(CN)2Br

  3. Rational design of organic superconductors through the use of the large, discrete molecular anions M(CF3)4-(M = Cu, Ag, Au) and SO3CF2CH2SF5-

    International Nuclear Information System (INIS)

    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(CF3)4- (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)2M(CF3)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(CF3)4- anion, and neutral 1,1,2- trihaloethane solvent molecule. Superconductivity has also been observed in an ET salt containing the discrete SF5CH2CF2SO3- anion with onset temperature near 5.2 K

  4. Video microscopic studies of an electrochemically-grown molecular crystal

    Science.gov (United States)

    Kobayashi, Y.; Fortune, N. A.

    1996-03-01

    We have adapted a trinocular microscope, CCD video camera and computer-interfaced video frame grabber to monitor and control the growth of molecular crystals in conventional and specially designed electrochemical cells. By digitally subtracting old images from new images, we are able to distinguish new growth from old growth and actively adjust external parameters during crystal growth. Our new electrochemical cell design not only improves our ability to optically study growth processes in the cell but also allows solution flow into and out of each cell chamber, providing the possibility of controlling anion composition and concentration over time. We are presently investigating how external parameters such as temperature, voltage and current density physically affect growth mechanisms. Applications include maintaining a constant crystal current density to maximize crystal size and quality for a given time interval, subject to additional constraints on the voltage across the electrochemical cell. At this conference, we report our progress to date in studying the growth of the prototypical molecular superconductor κ-(BEDT-TTF)_2Cu(NCS)_2.

  5. 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.

  6. Trifluoromethylmetallate anions as components of molecular charge transfer salts and superconductors.

    Energy Technology Data Exchange (ETDEWEB)

    Schlueter, J. A.

    1998-10-14

    Whereas polymeric and common inorganic anions frequently deprive the synthetic chemist of a chance to modify a charge transfer salt's structure through anion alterations, discrete organometallic anions provide a vast opportunity to probe the structure/property correlations of a material through rational synthetic methods. We have recently undertaken a research effort aimed at the crystallization of conducting charge transfer salts which possess modifiable, organometallic anions as the charge compensating entities. This research has been richly rewarded with the discovery of a new family of bis(ethylenedithio) tetrathiafulvalene (BEDT-TTF or ET) based molecular superconductors. Herein is presented a summary of over twenty {kappa}(ET){sub 2}M(CF{sub 3}){sub 4}(1,1,2-trihaloethane) (M = Cu, Ag, Au) superconducting salts. Three new related salts are also reported: (ET){sub 2} [trans-Ag(CF{sub 3}),(CN){sub 2}], {kappa}{sub L}(BEDT-TSF){sub 2}Ag(CF{sub 3}){sub 4}(TCE), and {kappa}{sub L}(ET){sub 2}Ag(CF{sub 3}){sub 3}Cl(TCE).

  7. 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.

  8. 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...

  9. 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.

  10. 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.

  11. Interplay between electronic and structural degrees of freedom in quarter-filled low dimensional conductors

    International Nuclear Information System (INIS)

    We review the basic aspects of the charge density wave (CDW) and bond order wave (BOW) instabilities observed in one dimension (1D) organic conductors at either the 2kF and/or 4kF critical wave vectors. We start by recalling the main features of the coupled structural/electronic Peierls instabilities observed in donor–acceptor (D–A) charge transfer (CT) salts. Then we consider the specific case of 2:1 salts D2X where X is a monovalent anion. We show that the incipient CDW/BOW instabilities of the Bechgaard and Fabre salts are those of the parent quarter-filled CT salts TMTSF-DMTCNQ and TMTTF-DMTCNQ respectively. We also consider more specifically the influence of specific features of D2X salts such as the stack dimerization, the Fermi surface warping and the coupling to the anions. Then we discuss more generally the role of the anions in the Bechgaard and Fabre salts by pointing out the influence of polarization and charge displacement induced by the anion shift. Finally we show that some of these features are also relevant to understand the subtle interplay between structural and electronic degrees of freedom in 2D quarter-filled organic salts such as the (BEDT-TTF)2X series

  12. 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...

  13. 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.

  14. 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

  15. 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

  16. 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