2,196 research outputs found
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
A simple construction of elliptic -matrices
We show that Belavin's solutions of the quantum Yang--Baxter equation can be
obtained by restricting an infinite -matrix to suitable finite dimensional
subspaces. This infinite -matrix is a modified version of the
Shibukawa--Ueno -matrix acting on functions of two variables.Comment: 6 page
Polynomial Realization of and Fusion Rules at Exceptional Values of
Representations of the algebra are constructed in the space of
polynomials of real (complex) variable for . The spin addition rule
based on eigenvalues of Casimir operator is illustrated on few simplest cases
and conjecture for general case is formulated
Self-organization of charge under pressure in the organic conductor (TMTSF)2ReO4
(TMTSF)2ReO4 presents a phase coexistence between two anion orderings defined
by their wave vectors q_2=(1/2,1/2,1/2) and q_3=(0,1/2,1/2) in a wide range of
pressure (8-11kbar) and temperature. From the determination of the anisotropy
of the conductivity and the superconducting transitions in this regime we were
able to extract the texture which results from a self-organization of the
orientations of the ReO4 anions in the sample. At the lowest pressures, the
metallic parts, related to the q_3 order, form droplets elongated along the
a-axis embedded in the semiconducting matrix associated with the q_2 order.
Above 10kbar, filaments along the a-axis extend from one end of the sample to
the other nearly up to the end of the coexistence regime. A mapping of the
system into an anisotropic Ising lattice is satisfactory to analyze the data.
satisfactory to analyze the data.Comment: 7 pages, 3 figures, EPL forma
Composition of Kinetic Momenta: The U_q(sl(2)) case
The tensor products of (restricted and unrestricted) finite dimensional
irreducible representations of \uq are considered for a root of unity.
They are decomposed into direct sums of irreducible and/or indecomposable
representations.Comment: 27 pages, harvmac and tables macros needed, minor TeXnical revision
to allow automatic TeXin
Two insulating phases in compressed Pr1-xCaxMnO3 thin films
The temperature dependent resistivity of two Pr1-xCaxMnO3 (x=0.5 and 0.4)
thin films grown on LaAlO3 has been studied as a function of hydrostatic
pressure (up to 2.5 GPa) and magnetic field (up to 9T). Both samples show a
monotonic decrease in the resistivity with an increase in pressure,
corresponding to a change of -35% at 2.5 GPa. No pressure induced
metal-to-insulator transition was observed in the temperature-dependent
resistivity. The non-trivial interaction between high pressure and magnetic
field reveals that the effect of pressure cannot be simply rescaled to that of
a specific field, as has been reported for the corresponding bulk material. We
propose an interpretation of the data based on phase separation, where two
different insulating phases coexist: the charge ordered phase, which is
sensitive to both magnetic field and pressure, and a second insulating phase
that can be tuned by magnetic field. Such a result demonstrates that phase
separation can be manipulated in thin films by independent application of
magnetic field and/or external pressure.Comment: 9 pages, 3 figuresn submitted to Applied Physics Letter
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