3,573 research outputs found
The Topological Relation Between Bulk Gap Nodes and Surface Bound States : Application to Iron-based Superconductors
In the past few years materials with protected gapless surface (edge) states
have risen to the central stage of condensed matter physics. Almost all
discussions centered around topological insulators and superconductors, which
possess full quasiparticle gaps in the bulk. In this paper we argue systems
with topological stable bulk nodes offer another class of materials with robust
gapless surface states. Moreover the location of the bulk nodes determines the
Miller index of the surfaces that show (or not show) such states. Measuring the
spectroscopic signature of these zero modes allows a phase-sensitive
determination of the nodal structures of unconventional superconductors when
other phase-sensitive techniques are not applicable. We apply this idea to
gapless iron based superconductors and show how to distinguish accidental from
symmetry dictated nodes. We shall argue the same idea leads to a method for
detecting a class of the elusive spin liquids.Comment: updated references, 6 pages, 4 figures, RevTex
Measurement of Refractive Index Change of Optical Fiber Core Induced by Femtosecond Laser Scanning
We report a new method to measure the refractive index change in optical fiber core induced by femtosecond (fs) laser exposure. An in-line Fabry-Perot interferometer, serving as the measurement platform, is constructed on a commercial single-mode optical fiber by onestep femtosecond (fs) laser fabrication. A positive refractive index change is observed and measured accurately as the laser pulse energy surpasses the ablation threshold
Innovative in silico approaches to address avian flu using grid technology
The recent years have seen the emergence of diseases which have spread very
quickly all around the world either through human travels like SARS or animal
migration like avian flu. Among the biggest challenges raised by infectious
emerging diseases, one is related to the constant mutation of the viruses which
turns them into continuously moving targets for drug and vaccine discovery.
Another challenge is related to the early detection and surveillance of the
diseases as new cases can appear just anywhere due to the globalization of
exchanges and the circulation of people and animals around the earth, as
recently demonstrated by the avian flu epidemics. For 3 years now, a
collaboration of teams in Europe and Asia has been exploring some innovative in
silico approaches to better tackle avian flu taking advantage of the very large
computing resources available on international grid infrastructures. Grids were
used to study the impact of mutations on the effectiveness of existing drugs
against H5N1 and to find potentially new leads active on mutated strains. Grids
allow also the integration of distributed data in a completely secured way. The
paper presents how we are currently exploring how to integrate the existing
data sources towards a global surveillance network for molecular epidemiology.Comment: 7 pages, submitted to Infectious Disorders - Drug Target
Scalar and Pseudoscalar Glueballs
We employ two simple and robust results to constrain the mixing matrix of the
isosinglet scalar mesons , , : one is the
approximate SU(3) symmetry empirically observed in the scalar sector above 1
GeV and confirmed by lattice QCD, and the other is the scalar glueball mass at
1710 MeV in the quenched approximation. In the SU(3) symmetry limit,
becomes a pure SU(3) octet and is degenerate with ,
while is mainly an SU(3) singlet with a slight mixing with the
scalar glueball which is the primary component of . These features
remain essentially unchanged even when SU(3) breaking is taken into account.
The observed enhancement of production over
in hadronic decays and the copious production in radiative
decays lend further support to the prominent glueball nature of
. We deduce the mass of the pseudoscalar glueball from an
-- mixing formalism based on the anomalous Ward identity for
transition matrix elements. With the inputs from the recent KLOE experiment, we
find a solution for the pseudoscalar glueball mass around GeV,
which is fairly insensitive to a range of inputs with or without
Okubo-Zweig-Iizuka-rule violating effects. This affirms that ,
having a large production rate in the radiative decay and not seen in
reactions, is indeed a leading candidate for the pseudoscalar
glueball. It is much lower than the results from quenched lattice QCD (
GeV) due to the dynamic fermion effect. It is thus urgent to have a full QCD
lattice calculation of pseudoscalar glueball masses.Comment: 10 pages, 1 figure; talk presented at "Particle Physics, Astrophysics
and Quantum Field Theory: 75 Years since Solvay", November 27-29, 2008,
Singapor
Broadband energy-efficient optical modulation by hybrid integration of silicon nanophotonics and organic electro-optic polymer
Silicon-organic hybrid integrated devices have emerging applications ranging
from high-speed optical interconnects to photonic electromagnetic-field
sensors. Silicon slot photonic crystal waveguides (PCWs) filled with
electro-optic (EO) polymers combine the slow-light effect in PCWs with the high
polarizability of EO polymers, which promises the realization of
high-performance optical modulators. In this paper, a broadband,
power-efficient, low-dispersion, and compact optical modulator based on an EO
polymer filled silicon slot PCW is presented. A small voltage-length product of
V{\pi}*L=0.282Vmm is achieved, corresponding to an unprecedented record-high
effective in-device EO coefficient (r33) of 1230pm/V. Assisted by a backside
gate voltage, the modulation response up to 50GHz is observed, with a 3-dB
bandwidth of 15GHz, and the estimated energy consumption is 94.4fJ/bit at
10Gbit/s. Furthermore, lattice-shifted PCWs are utilized to enhance the optical
bandwidth by a factor of ~10X over other modulators based on
non-band-engineered PCWs and ring-resonators.Comment: 12 pages, 4 figures, SPIE Photonics West Conference 201
Phosphorus Accumulation in Soil Surface under Japanese Lawngrass (\u3cem\u3eZoysia japonica\u3c/em\u3e Steud.) Pasture
A SOCIAL SURVEY ON COMMUNITY RESPONSE TO ROAD TRAFFIC NOISE IN HANOI
Joint Research on Environmental Science and Technology for the Eart
Nature of magnetic coupling between Mn ions in as-grown GaMnAs studied by x-ray magnetic circular dichroism
The magnetic properties of as-grown GaMnAs have been
investigated by the systematic measurements of temperature and magnetic field
dependent soft x-ray magnetic circular dichroism (XMCD). The {\it intrinsic}
XMCD intensity at high temperatures obeys the Curie-Weiss law, but residual
spin magnetic moment appears already around 100 K, significantly above Curie
temperature (), suggesting that short-range ferromagnetic correlations are
developed above . The present results also suggest that antiferromagnetic
interaction between the substitutional and interstitial Mn (Mn) ions
exists and that the amount of the Mn affects .Comment: 4 pages, 4 figure
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