927 research outputs found
Purification of 2,3,6,7,10,11-hexamethoxytriphenylene and Preparation of hexakiscarbonylmethyl and hexakiscyanomethyl derivatives of 2,3,6,7,10,11-hexahydroxytriphenylene
Suppression of superconductivity by non-magnetic disorder in the organic superconductor (TMTSF)2(ClO4)(1-x)(ReO4)x
We present a study of the superconducting properties (Tc and Hc2) in the
solid solution (TMTSF)2(ClO4)(1-x)(ReO4)x with a ReO-4 nominal concentration up
to x = 6%. The dramatic suppression of Tc when the residual resistivity is
increased upon alloying with no modification of the Fermi surface is the
signature of non-conventional superconductivity . This behaviour strongly
supports p or d wave pairing in quasi one dimensional organic superconductors.
The determination of the electron lifetime in the normal state at low
temperature confirms that a single particle Drude model is unable to explain
the temperature dependence of the conductivity and that a very narrow zero
frequency mode must be taken into account for the interpretation of the
transport properties.Comment: Received 26 January 2004 / Received in final form 17 June 2004 /
Published online 3 August 200
Coexistence of Superconductivity and Spin Density Wave orderings in the organic superconductor (TMTSF)_2PF_6
The phase diagram of the organic superconductor (TMTSF)_2PF_6 has been
revisited using transport measurements with an improved control of the applied
pressure. We have found a 0.8 kbar wide pressure domain below the critical
point (9.43 kbar, 1.2 K) for the stabilisation of the superconducting ground
state featuring a coexistence regime between spin density wave (SDW) and
superconductivity (SC). The inhomogeneous character of the said pressure domain
is supported by the analysis of the resistivity between T_SDW and T_SC and the
superconducting critical current. The onset temperature T_SC is practically
constant (1.20+-0.01 K) in this region where only the SC/SDW domain proportion
below T_SC is increasing under pressure. An homogeneous superconducting state
is recovered above the critical pressure with T_SC falling at increasing
pressure. We propose a model comparing the free energy of a phase exhibiting a
segregation between SDW and SC domains and the free energy of homogeneous
phases which explains fairly well our experimental findings.Comment: 13 pages, 10 figures, revised v: fig.9 added, section 4.2 rewritten,
accepted v: sections 4&5 improve
Influence of Quantum Hall Effect on Linear and Nonlinear Conductivity in the FISDW States of the Organic Conductor (TMTSF)_2PF_6
We report a detailed characterization of quantum Hall effect (QHE) influence
on the linear and non-linear resistivity tensor in FISDW phases of the organic
conductor (TMTSF)2PF6. We show that the behavior at low electric fields,
observed for nominally pure single crystals with different values of the
resistivity ratio, is fully consistent with a theoretical model, which takes
QHE nature of FISDW and residual quasi-particle density associated with
different crystal imperfection levels into account. The non-linearity in
longitudinal and diagonal resistivity tensor components observed at large
electric fields reconciles preceding contradictory results. Our theoretical
model offers a qualitatively good explanation of the observed features if a
sliding of the density wave with the concomitant destruction of QHE, switched
on above a finite electric field, is taken into account.Comment: 8 pages, 6 figures, submitted to EPJ
Nodal Superconducting Order Parameter and Thermodynamic Phase Diagram of (TMTSF)2ClO4
The organic materials (TMTSF)2X are unique unconventional superconductors
with archetypal quasi-one-dimensional (Q1D) electronic structures. Here, based
on our comprehensive field-angle-resolved calorimetry of (TMTSF)2ClO4, we
succeeded in mapping the nodal gap structure for the first time in Q1D systems,
by discriminating between the Fermi wavevectors and Fermi velocities. In
addition, the thermodynamic phase diagrams of (TMTSF)2ClO4 for all principal
field directions are obtained. These findings, providing strong evidence of
nodal spin-singlet superconductivity, serves as solid bases for further
elucidation of anomalous superconducting phenomena in (TMTSF)2X.Comment: 7 pages, 7 figures, including Supplemental Information added at the
end of the manuscrip
Two Intranasal Administration Techniques Give Two Different Pharmacokinetic Results
Minor changes in the administration technique used for intranasal instillation of clonazepam, have been found to influence the results significantly. A simple study was performed, where rabbits received 0.5 mg clonazepam intranasally. One group received the drug while fixed in a sitting position, where the other group was fixed in a supine position. The results show that both techniques where able to provide a rapid absorption with a tmax around 3-4 min. The Cmax and AUC, however, were very different. The Cmax was found to be 40 ng/ml and 86 ng/ml, respectively, and the AUC was found to be 891 and 2249 (ng/ml/min), respectively, for the sitting and the supine position. The relative bioavailability for sitting/supine was found to be 38%. These results show that the administration technique is very important and should not be underestimated.
Mechanism of confinement in low-dimensional organic conductors
Confinement-deconfinement transition in quarter-filled two-coupled chains
comprising dimerization, repulsive interactions and interchain hopping has been
demonstrated by applying the renormalization group method to the bosonized
Hamiltonian. The confinement given by the irrelevant interchain hopping occurs
with increasing umklapp scattering which is induced by the dimerization leading
to effectively half-filling. It is shown that the transition originates in a
competition between a charge gap and the renormalized interchain hopping.Comment: 5 pages, 7 figures, Proc. CREST Int. Workshop, Nagoya 2000, submitted
to J. Phys. Chem. Solid
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