178,607 research outputs found
Anisotropy and interaction effects of strongly strained SrIrO3 thin films
Magneto-transport properties of SrIrO thin films epitaxially grown on
SrTiO, using reactive RF sputtering, are investigated. A large anisotropy
between the in-plane and the out-of-plane resistivities is found, as well as a
signature of the substrate cubic to tetragonal transition. Both observations
result from the structural distortion associated to the epitaxial strain. The
low-temperature and field dependences of the Hall number are interpreted as due
to the contribution of Coulomb interactions to weak localization, evidencing
the strong correlations in this material. The introduction of a contribution
from magnetic scatters, in the analysis of magnetoconductance in the weakly
localized regime, is proposed as an alternative to an anomalously large
temperature dependence of the Land\'{e} coefficient
Influence of Disorder on the Hall Effect in BiSrCuO
The in-plane resistivity and Hall coefficient have been measured for the
single-layer compound BiSrCuO for the whole range of
doping states. The deviation of the Hall coefficient, , from a
high-temperature linear behavior and the temperature dependence of the Hall
angle are both only weakly dependent upon doping, contrasting with
BiSrLaCuO and BiSrCaCuO. This
is in contradiction with former proposals that the transverse transport detects
the formation of incoherent Cooper pairs in the pseudogap state. Conversely,
the analysis of the data using a phenomenological angular dependent scattering
rate clearly allows to distinguish between underdoped and overdoped states, and
we propose that the maximum in simply arises due to the combination of
a large isotropic scattering rate and an anisotropic temperature dependent one
Binary Stellar Population Synthesis Model
Using Yunnan evolutionary population synthesis (EPS) models, we present
integrated colours, integrated spectral energy distributions (ISEDs) and
absorption-line indices defined by the Lick Observatory image dissector scanner
(Lick/IDS) system, for an extensive set of instantaneous-burst binary stellar
populations (BSPs) with interactions. By comparing the results for populations
with and without interactions we show that the inclusion of binary interactions
makes the appearance of the population substantially bluer. This effect raises
the derived age and metallicity of the population.
To be used in the studies of modern spectroscopic galaxy surveys at
intermediate/high spectral resolution, we also present intermediate- (3A) and
high-resolution (~0.3A) ISEDs and Lick/IDS absorption-line indices for BSPs. To
directly compare with observations the Lick/IDS absorption indices are also
presented by measuring them directly from the ISEDs.Comment: 2 pages 2 figure
Analysis of the strong coupling constant and the decay width of with QCD sum rules
In this article, we calculate the form factors and the coupling constant of
the vertex using the three-point QCD sum rules. We
consider the contributions of the vacuum condensates up to dimension in the
operator product expansion(OPE). And all possible off-shell cases are
considered, , and , resulting in three different form
factors. Then we fit the form factors into analytical functions and extrapolate
them into time-like regions, which giving the coupling constant for the
process. Our analysis indicates that the coupling constant for this vertex is
. The results of this work are very useful
in the other phenomenological analysis. As an application, we calculate the
coupling constant for the decay channel and
analyze the width of this decay with the assumption of the vector meson
dominance of the intermediate . Our final result about the decay
width of this decay channel is .Comment: arXiv admin note: text overlap with arXiv:1501.03088 by other author
Resistance noise in Bi_2Sr_2CaCu_2O
The resistance noise in a Bi_2Sr_2CaCu_2O thin film is found to
increase strongly in the underdoped regime. While the increase of the raw
resistance noise with decreasing temperature appears to roughly track the
previously reported pseudogap temperature for this material, standard noise
analysis rather suggests that the additional noise contribution is driven by
the proximity of the superconductor-insulator transition
Anisotropy of the in-plane angular magnetoresistance of electron-doed Sr1-xLaxCuO2 thin films
Signatures of antiferromagnetism (AF) in the underdoped Ln2-xCexCuO4 (Ln =
Nd, Pr,...) family are observed even for doping levels for which
superconductivity exists. We have looked for a similar property in a different
electron-doped cuprate family, Sr1-xLaxCuO2, which consists of CuO2 planes
separated by Sr/La atoms, and is exempt of the possible influence of magnetic
rare earth ions. We report in-plane magnetoresistance measurements in the
normal state of underdoped, superconducting, c-axis oriented, epitaxial
Sr1-xLaxCuO2 thin films. This probe is sensitive to spin arrangement and we
find that the in-plane magnetoresistance, which is negative and does not
saturate for T, exhibits an angular dependence when measured upon rotating a
magnetic field within the CuO2 planes. The analysis reveals a superposition of
fourfold and twofold angular oscillations. Both of these increase in amplitude
with increasing field and decreasing and appear below a temperature, which gets
higher with decreasing doping levels. Our results demonstrate that these
magnetoresistance oscillations, also observed for the Ln2-xCexCuO4 (Ln = Nd,
Pr,...) family and attributed to an AF signature, are, without ambiguity, a
property of CuO2 planes. Besides, these oscillations vary with doping in an
unusual way compared to previous results: fourfold oscillations are essentially
present in the more underdoped samples while only twofold oscillations are
visible in the less underdoped ones. This intriguing observation appears to be
a consequence of spin dilution with increasing doping level.Comment: 25 pages, 6 figure
QED Penguin Contributions To Isospin Splittings of Heavy-Light Quark Systems
Recent experiments show that the isospin-violating mass splitting of the B
mesons is very small, but the best fits with a QCD sum rule analysis give a
splitting of at least 1.0 MeV. The isospin-violating mass splittings of the
charmed mesons, on the other hand, are in agreement with experiment. In this
letter we show that the inclusion of 2 kind QED penguin diagrams can
account for this discrepancy within the errors in the QCD sum rule method.Comment: 9 pages, latex, 2 figure
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