385 research outputs found
Infrared study on the formation of charge density waves in (TMTSF) 2X (X = Reo4− and PF6− at atmospheric pressure
No full textUnconventional spin density wave in Bechgaard salt
No full textThe quasi–one-dimensional organic conductor Bechgaard salts
\chem{(TMTSF)_2}X with \chem{X}=\chem{PF_6}, \chem{ClO_4},
\chem{AsF_6}, etc. are well known for the variety of their
ground states: spin density wave (SDW), field-induced spin
density wave (FISDW) and triplet superconductivity. We propose
here that the unconventional spin density wave (USDW) occupies a
large area of the P-B phase diagram, where SDW is suppressed
by pressure (P) and superconductivity by magnetic field (B)
and FISDW is still absent. USDW describes the striking angular
dependent magnetoresistance (ADMR) seen in this area of the phase
diagram, when the magnetic field is rotated in the
c*- plane. Also the Lebed resonances are naturally
interpreted in terms of the imperfect nesting term
Conduction anisotropy of the Bechgaard salts
No full textWe report the results of a systematic study on the temperature dependence of the normal state conductivity, measured along the a, b', and c* axis, in a representative set of Bechgaard salts. The anisotropic electron transport of four compounds are compared : (TMTSF)2ClO4, (TMTSF)2PF6, (TMTTF)2Br and (TMTTF)2PF6. We analyze the tendency, following this order of the compounds, of the metallic ab' plane conductivity change to a semiconductor like behavior, and we discuss the mechanism of inter- and intra-chain transport. The c*-direction conduction is determined by the nature of the counter-ion and seems to be irrelevant in this comparison
Magnetic properties of an organic Mott insulator. Separate donor and acceptor phase transitions in hexamethylenetetrathiafulvalene tetrafluorotetracyano-quinodimethane (HMTTF-TCNQF_{4})
No full textNon magnetic anion substitution in (TMTSF)<sub>2</sub>ClO<sub>4</sub>: Consequences on the superconductivity
No full textNon magnetic impurities substitution is a method to check
the microscopic origin of superconductivity. In (TMTSF)ClO, we
substitute a small fraction of the ClO anions by ReO. The anion
ordering temperature is shown to be unaffected by alloying in the explored
range 0-3.1%. However, the critical temperature is strongly reduced with
increased residual resistivity obtained through alloying and/or increased
speed of cooling. Our results are compatible with an unconventional
superconductivity in the Bechgaard salts.
Key words. Bechgaard salts – unconventional superconductivity –
alloys
NMR studies of the exotic members of the Bechgaard salts, NO3 and FSO3 salts
No full text1H, 19F and 77Se NMR measurements were performed to investigate the properties of Bechgaard salts, (TMTSF) 2X, with noncentrosymmetric anions, X=NO3 and FSO 3. Single crystal 77Se NMR signal for NO3 salt detects the spin density wave transition. Preliminary analyses of the angular dependence of 1H NMR spectra were also carried out. Spin density wave in the NO3 salt was confirmed to have an incommensurate wave number and relatively small amplitude. 19F and 77Se NMR signals in the FSO3 salt could detect drastic anomaly at the anion ordering temperature. The insulating state was confirmed to be nonmagnetic with a large spin gap of 420 K. © 2003 Published by Elsevier Science B.V
Observation of Shubnikov-de Haas oscillations in the quasi-one-dimensional Bechgaard salt (TMTSF)2FSO3
No full textThe longitudinal magnetoresistance of the unusual Bechgaard salt, (TMTSF)2FSO3, has been studied up to 33 T under various pressures. In this compound, a single series of the Shubnikov-de Haas (SdH) oscillation is very pronounced for pressures between 5.2 and 11.8 kbar where the zero-field ground state is superconducting. Unlike the case of the rapid oscillations in most Bechgaard salts, the temperature and magnetic field dependence of the oscillations is in good agreement with the Lifshitz-Kosevich formula, implying the two-dimensional closed orbital motion of the electrons. The effective mass of the electrons and Dingle temperature are estimated as 1.4 ± 0.05 m0 and 1.6-2.4 K, respectively. For an origin of the closed orbits, it is suggested that incomplete nesting between open Fermi surfaces is induced by pressure. Discontinuous change of the frequency, amplitude, and Dingle temperature of the oscillations around 9 kbar indicates that the electronic state below and above this pressure is different. According to the features of the SdH oscillations along with the phase diagram of (TMTSF)2FSO3, the pressure dependence is divided into three regions
Optical and photoemission evidence for a Tomonaga-Luttinger liquid in the Bechgaard salts
No full textCombined optical and photoemission experiments on the quasi-one dimensional Bechgaard salts reveal the non-Fermi liquid character of these prototype quasi-one dimensional interacting electron systems. We show that various aspects of the exotic normal state properties along the chains are consistent with the predictions of the Tomonaga-Luttinger liquid theory. We also discuss the effect of interchain coupling on the insulator-metal transition, associated with the electron confinement-deconfinement crossover.LS
Optical and photoemission evidence for a Tomonaga-Luttinger liquid in the Bechgaard salts
No full textCombined optical and photoemission experiments on the quasi-one dimensional
Bechgaard salts reveal the non-Fermi liquid character of these prototype quasi-one
dimensional interacting electron systems. We show that various aspects of the exotic
normal state properties along the chains are consistent with the predictions of the
Tomonaga-Luttinger liquid theory. We also discuss the effect of interchain coupling
on the insulator-metal transition, associated with the electron
confinement-deconfinement crossover
Optical and photoemission evidence for a Tomonaga-Luttinger liquid in the Bechgaard salts
No full textAbstract. Combined optical and photoemission experiments on the quasi-one dimensional Bechgaard salts reveal the non-Fermi liquid character of these prototype quasi-one dimensional interacting electron systems. We show that various aspects of the exotic normal state properties along the chains are consistent with the predictions of the Tomonaga-Luttinger liquid theory. We also discuss the effect of interchain coupling on the insulator-metal transition, associated with the electron confinement-deconfinement crossover. PACS. 78.20.-e Optical properties of bulk materials and thin films -79.60.-i Photoemission and photoelectron spectra -71.27.+a Strongly correlated electron systems; heavy fermion
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