368 research outputs found
Impurity-induced in-gap state and Tc in sign-reversing s-wave superconductors: analysis of iron oxypnictide superconductors
The sign-reversing fully gapped superconducting state, which is expected to
be realized in oxypnictide superconductors, can be prominently affected by
nonmagnetic impurities due to the interband scattering of Cooper pairs. We
study this problem based on the isotropic two-band BCS model: In oxypnictide
superconductors, the interband impurity scattering is not equal to the
intraband one . In the Born scattering regime, the reduction in Tc is
sizable and the impurity-induced density of states (DOS) is prominent if , due to the interband scattering. Although impurity-induced DOS can yield a
power-law temperature dependence in , a sizable suppression in Tc is
inevitably accompanied. In the unitary scattering regime, in contrast, impurity
effect is very small for both Tc and DOS except at . By comparing theory
and experiments, we expect that the degree of anisotropy in the -wave
gap function strongly depends on compounds.Comment: 16 pages, 5 figures, to be published in New. J. Phy
Spectral evolution in (Ca,Sr)RuO_3 near the Mott-Hubbard transition
We investigated the optical properties of (Ca,Sr)RuO_3 films on the
borderline of a metal-insulator (M-I) transition. Our results show all of the
predicted characteristics for a metallic Mott-Hubbard system, including (i) a
mass enhancement in dc-limit, (ii) an U/2 excitation, and (iii) an U
excitation. Also, a self-consistency is found within the
Gutzwiller-Brinkman-Rice picture for the Mott transition. Our finding displays
that electron correlation should be important even in 4d materials.Comment: REVTEX 4 pages, 5 EPS figures, submitted to Phys. Rev. Let
In-plane Tunneling Spectrum into a [110]-Oriented High- Superconductor in the Pseudogap Regime
Both the differential tunneling conductance and the surface local density of
states (LDOS) of a [110]-oriented high-temperature superconductor in the
pseudogap (PG) regime are studied theoretically. As a competing candidate for
the mechanism of PG state, the charge-density wave (CDW), spin-density wave
(SDW), -density wave (DDW), and d-wave superconducting (DSC) orderings show
distinct features in the tunneling conductance. For the CDW, SDW, and DSC
orderings, the tunneling conductance approaches the surface LDOS as the barrier
potential is increased. For the DDW ordering, we show for the first time that
there exist midgap states at the [110] surface, manifesting themselves as a
sharp zero-energy peak in the LDOS, as in the case of DSC ordering. However,
due to the particle-hole pair nature of the DDW state, these states do not
carry current, and consequently the one-to-one correspondence between the
tunneling conductance and the surface LDOS is absent.Comment: 5 pages, 4 figures embedded in the tex
Nuclear magnetic relaxation and superfluid density in Fe-pnictide superconductors: An anisotropic \pm s-wave scenario
We discuss the nuclear magnetic relaxation rate and the superfluid density
with the use of the effective five-band model by Kuroki et al. [Phys. Rev.
Lett. 101, 087004 (2008)] in Fe-based superconductors. We show that a
fully-gapped anisotropic \pm s-wave superconductivity consistently explains
experimental observations. In our phenomenological model, the gaps are assumed
to be anisotropic on the electron-like \beta Fermi surfaces around the M point,
where the maximum of the anisotropic gap is about four times larger than the
minimum.Comment: 10 pages, 8 figures; Submitted versio
Waterproof Flexible InP@ZnSeS Quantum Dot Light-Emitting Diode
The development of flexible displays for wearable electronics applications has created
demand for high-performance quantum dot (QD) light-emitting diodes (QLEDs) based on QD
core@shell structures. Emerging indium phosphide (InP)-based core@shell QDs show
promise as lighting material in the field of optoelectronics because they are environmentally
friendly material, can be produced in a cost-effective manner, and are capable of tunable
emission. While efforts have been made to enhance the performance of InP-based QLED, the
stabilities of InP@ZnSeS QDs film and InP@ZnSeS-based QLED in water/air are not yet
fully understood, limiting their practical applications. Herein, a highly durable, flexible
InP@ZnSeS QLED encapsulated in an ultrathin film of CYTOP, a solution-based amorphous
fluoropolymer, is demonstrated. The CYTOP-encapsulated green flexible QLED shows an
external quantum efficiency (EQE) of 0.904% and a high luminescence of 1593 cd/m2
as
well as outstanding waterproof performance. The flexible device emits strong luminescence
after being immersed in water for ~20 minutes. Even when subjected to continuous tensile
stress with a 5 mm bending radius, the high luminescence is preserved. This waterproof
architecture can be a promising strategy for wearable electronics applications
Pseudogap formation of four-layer BaRuO and its electrodynamic response changes
We investiaged the optical properties of four-layer BaRuO, which shows
a fermi-liquid-like behavior at low temperature. Its optical conductivity
spectra clearly displayed the formation of a pseudogap and the development of a
coherent peak with decreasing temperature. Temperature-dependences of the
density and the scattering rate of the coherent component were
also derived. As the temperature decreases, both and decrease for
four-layer BaRuO. These electrodynamic responses were compared with those
of nine-layer BaRuO, which also shows a pseudogap formation but has an
insulator-like state at low temperature. It was found that the relative rates
of change of both and determine either metallic or insulator-like
responses in the ruthenates. The optical properties of the four-layer ruthenate
were also compared with those of other pseudogap systems, such as high
cuprates and heavy electron systems.Comment: 7 figures. submitted to Phys. Rev.
Discovering study-specific gene regulatory networks
This article has been made available through the Brunel Open Access Publishing Fund.Microarrays are commonly used in biology because of their ability to simultaneously measure thousands of genes under different conditions. Due to their structure, typically containing a high amount of variables but far fewer samples, scalable network analysis techniques are often employed. In particular, consensus approaches have been recently used that combine multiple microarray studies in order to find networks that are more robust. The purpose of this paper, however, is to combine multiple microarray studies to automatically identify subnetworks that are distinctive to specific experimental conditions rather than common to them all. To better understand key regulatory mechanisms and how they change under different conditions, we derive unique networks from multiple independent networks built using glasso which goes beyond standard correlations. This involves calculating cluster prediction accuracies to detect the most predictive genes for a specific set of conditions. We differentiate between accuracies calculated using cross-validation within a selected cluster of studies (the intra prediction accuracy) and those calculated on a set of independent studies belonging to different study clusters (inter prediction accuracy). Finally, we compare our method's results to related state-of-the art techniques. We explore how the proposed pipeline performs on both synthetic data and real data (wheat and Fusarium). Our results show that subnetworks can be identified reliably that are specific to subsets of studies and that these networks reflect key mechanisms that are fundamental to the experimental conditions in each of those subsets
Modern microwave methods in solid state inorganic materials chemistry: from fundamentals to manufacturing
No abstract available
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