210 research outputs found
The diamagnetism above the superconducting transition in underdoped La(1.9)Sr(0.1)CuO(4) revisited: Chemical disorder or phase incoherent superconductivity?
The interplay between superconducting fluctuations and inhomogeneities
presents a renewed interest due to recent works supporting an anomalous [beyond
the conventional Gaussian-Ginzburg-Landau (GGL) scenario] diamagnetism above Tc
in underdoped cuprates. This conclusion, mainly based in the observation of new
anomalies in the low-field isothermal magnetization curves, is in contradiction
with our earlier results in the underdoped La(1.9)Sr(0.1)CuO(4) [Phys. Rev.
Lett. 84, 3157 (2000)]. These seemingly intrinsic anomalies are being presented
in various influential works as a 'thermodynamic evidence' for phase incoherent
superconductivity in the pseudogap regime, this last being at present a central
and debated issue of the cuprate superconductors' physics. Here we have
extended our magnetization measurements in La(1.9)Sr(0.1)CuO(4) to two samples
with different chemical disorder, in one of them close to the one associated
with the random distribution of Sr ions. For this sample, the corresponding
Tc-distribution may be approximated as symmetric around the average Tc, while
in the most disordered sample is strongly asymmetric. The comparison between
the magnetization measured in both samples provides a crucial check of the
chemical disorder origin of the observed diamagnetism anomalies, which are
similar to those claimed as due to phase fluctuations by other authors. This
conclusion applies also to the sample affected only by the intrinsic-like
chemical disorder, providing then a further check that the intrinsic
diamagnetism above the superconducting transition of underdoped cuprates is not
affected by the opening of a pseudogap in the normal state. It is also shown
here that once these disorder effects are overcome, the remaining precursor
diamagnetism may be accounted at a quantitative level in terms of the GGL
approach under a total energy cutoff.Comment: 13 pages, 7 figures. Minor corrections include
Observation of anisotropic diamagnetism above the superconducting transition in iron-pnictide Ba_(1-x)K_xFe2As2 single crystals due to thermodynamic fluctuations
High resolution magnetization measurements performed in a high quality
Ba_(1-x)K_xFe2As2 single crystal allowed to determine the diamagnetism induced
above the superconducting transition by thermally activated Cooper pairs. These
data, obtained with magnetic fields applied along and transverse to the crystal
ab layers, demonstrate experimentally that the superconducting transition of
iron pnictides may be explained at a phenomenological level in terms of the
Gaussian Ginzburg-Landau approach for three-dimensional anisotropic
superconductors.Comment: Final version with minor corrections. 6 pages, 4 figure
Cassini ISS astrometry of the Saturnian satellites: Tethys, Dione, Rhea, Iapetus, and Phoebe 2004-2012
This work was mainly funded by European Community’s
Seventh Framework Program (FP7/2007-2013) under grant agreement 263466
for the FP7-ESPaCE, and partially by UPMC-EMERGENCE (contract number
EME0911), for which R.T. and V.L. are grateful. R.T. was also supported
by the Cassini mission. In addition, this work was supported by the Science
and Technology Facilites Council (Grant No. ST/F007566/1) and C.D.M. and
N.J.C. are grateful to them for financial assistance. C.D.M. is also grateful to
the Leverhulme Trust for the award of a Research Fellowship
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