37,766 research outputs found
Feasibility of Experimental Realization of Entangled Bose-Einstein Condensation
We examine the practical feasibility of the experimental realization of the
so-called entangled Bose-Einstein condensation (BEC), occurring in an entangled
state of two atoms of different species. We demonstrate that if the energy gap
remains vanishing, the entangled BEC persists as the ground state of the
concerned model in a wide parameter regime. We establish the experimental
accessibility of the isotropic point of the effective parameters, in which the
entangled BEC is the exact ground state, as well as the consistency with the
generalized Gross-Pitaevskii equations. The transition temperature is
estimated. Possible experimental implementations are discussed in detail.Comment: 6 pages, published versio
Large Area Roller Embossing of Multilayered Ceramic Green Composites
In this paper, we will report our achievements in developing large area
patterning of multilayered ceramic green composites using roller embossing. The
aim of our research is to pattern large area ceramic green composites using a
modified roller laminating apparatus, which is compatible with screen printing
machines, for integration of embossing and screen printing. The instrumentation
of our roller embossing apparatus, as shown in Figure1, consists of roller 1
and rollers 2. Roller 1 is heated up to the desired embossing temperature ;
roller 2 is, however, kept at room temperature. The mould is a nickel template
manufactured by plating nickel-based micro patterns (height : 50 m) on a
nickel film (thickness : 70 m) ; the substrate for the roller embossing is
a multilayered Heraeus Heralock HL 2000 ceramic green composite. Comparing with
the conventional simultaneous embossing, the advantages of roller embossing
include : (1) low embossing force ; (2) easiness of demoulding ; (3) localized
area in contact with heater ; and etc. We have demonstrated the capability of
large area roller embossing with a panel size of 150mmx 150mm on the mentioned
substrate. We have explored and confirmed the impact of parameters (feed speed,
temperature of roller and applied pressure) to the pattern quality of roller
embossing. Furthermore, under the optimized process parameters, we
characterized the variations of pattern dimension over the panel area, and
calculated a scaling factor in order to make the panel compatible with other
processes. Figure 2 shows the embossed patterns on a 150mmx 150mm green ceramic
panel.Comment: Submitted on behalf of EDA Publishing Association
(http://irevues.inist.fr/handle/2042/16838
Observation of strong-coupling pairing with weakened Fermi-surface nesting at optimal hole doping in CaNaFeAs
We report an angle-resolved photoemission investigation of optimally-doped
CaNaFeAs. The Fermi surface topology of this compound
is similar to that of the well-studied BaKFeAs
material, except for larger hole pockets resulting from a higher hole
concentration per Fe atoms. We find that the quasi-nesting conditions are
weakened in this compound as compared to BaKFeAs. As
with BaKFeAs though, we observe nearly isotropic
superconducting gaps with Fermi surface-dependent magnitudes. A small variation
in the gap size along the momentum direction perpendicular to the surface is
found for one of the Fermi surfaces. Our superconducting gap results on all
Fermi surface sheets fit simultaneously very well to a global gap function
derived from a strong coupling approach, which contains only 2 global
parameters.Comment: 5 pages, 4 figure
High-concentration Er:YAG single-crystal fibers grown by laser-heated pedestal growth technique
High-concentration Er:YAG single-crystal fibers have been grown using the laser-heated pedestal growth technique. Instability in the melt and concomitant opacity of fibers were observed at source concentrations higher than 15 mol.%. Spectroscopic examination shows that broadening of the linewidth of the I<sub>13/2</sub>4→I<sub>15/2</sub>4 transition is strongly dependent on Er<sup>3+</sup> concentration
Enhancement of Transition Temperature in FexSe0.5Te0.5 Film via Iron Vacancies
The effects of iron deficiency in FexSe0.5Te0.5 thin films (0.8<x<1) on
superconductivity and electronic properties have been studied. A significant
enhancement of the superconducting transition temperature (TC) up to 21K was
observed in the most Fe deficient film (x=0.8). Based on the observed and
simulated structural variation results, there is a high possibility that Fe
vacancies can be formed in the FexSe0.5Te0.5 films. The enhancement of TC shows
a strong relationship with the lattice strain effect induced by Fe vacancies.
Importantly, the presence of Fe vacancies alters the charge carrier population
by introducing electron charge carriers, with the Fe deficient film showing
more metallic behavior than the defect-free film. Our study provides a means to
enhance the superconductivity and tune the charge carriers via Fe vacancy, with
no reliance on chemical doping.Comment: 15 pages, 4 figure
Chaotic Amplification of Neutrino Chemical Potentials by Neutrino Oscillations in Big Bang Nucleosynthesis
We investigate in detail the parameter space of active-sterile neutrino
oscillations that amplifies neutrino chemical potentials at the epoch of Big
Bang Nucleosynthesis. We calculate the magnitude of the amplification and show
evidences of chaos in the amplification process. We also discuss the
implications of the neutrino chemical potential amplification in the Big Bang
Nucleosynthesis. It is shown that with a eV \nue, the amplification
of its chemical potential by active-sterile neutrino oscillations can lower the
effective number of neutrino species at Big Bang Nucleosynthesis to
significantly below 3.Comment: Revtex 20 pages, 7 postscript figures. Also by
ftp://astro.queensu.ca/pub/shi/ . Submitted to PR
Spatial distribution of local currents of massless Dirac fermions in quantum transport through graphene nanoribbons
We employ the formalism of bond currents, expressed in terms of the
nonequilibrium Green functions, to image the charge flow between two sites of
the honeycomb lattice of graphene ribbons of few nanometers width. In sharp
contrast to nonrelativistic electrons, current density profiles of quantum
transport at energies close to the Dirac point in clean zigzag graphene
nanoribbons (ZGNR) differs markedly from the profiles of charge density peaked
at the edges due to zero-energy localized edge states. For transport through
the lowest propagating mode induced by these edge states, edge vacancies do not
affect current density peaked in the center of ZGNR. The long-range potential
of a single impurity acts to reduce local current around it while concurrently
increasing the current density along the zigzag edge, so that ZGNR conductance
remains perfect .Comment: 5 pages, 5 figure
The Calculation of Vacuum Properties from the Global Color Symmetry Model
A modified method for calculating the non-perturbative quark vacuum
condensates from the global color symmetry model is derived. Within this
approach it is shown that the vacuum condensates are free of ultraviolet
divergence which is different from previous studies. As a special, the
two-quark condensate and the mixed quark-gluon condensate are calculated. A
comparision with the results of the other nonperturbative QCD approaches is
given.Comment: 17 page
(D* to D + gamma) and (B* to B + gamma) as derived from QCD Sum Rules
The method of QCD sum rules in the presence of the external electromagnetic
field is used to analyze radiative decays of charmed or bottomed
mesons such as and , with the
susceptibilities obtained previously from the study of baryon magnetic moments.
Our predictions on decays agree very well with the experimental
data. There are differences among the various theoretical predictions on
decays but the data are not yet available.Comment: 11 pages, Late
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