41,877 research outputs found
Efficient excitation and tuning of toroidal dipoles within individual homogenous nanoparticles
We revisit the fundamental topic of light scattering by single homogenous
nanoparticles from the new perspective of excitation and manipulation of
toroidal dipoles. It is revealed that besides within all-dielectric particles,
toroidal dipoles can also be efficiently excited within homogenous metallic
nanoparticles. Moreover, we show that those toroidal dipoles excited can be
spectrally tuned through adjusting the radial anisotropy parameters of the
materials, which paves the way for further more flexible manipulations of the
toroidal responses within photonic systems. The study into toroidal multipole
excitation and tuning within nanoparticles deepens our understanding of the
seminal problem of light scattering, and may incubate many scattering related
fundamental researches and applications.Comment: Four Figures,Ten Pages and Comments Welcome
Elusive pure anapole excitation in homogenous spherical nanoparticles with radial anisotropy
For homogenous isotropic dielectric nanospheres with incident plane waves,
Cartesian electric and toroidal dipoles can be tunned to cancel each other in
terms of far-field scattering, leading to the effective anopole excitation. At
the same time however, other multipoles such as magnetic dipoles with
comparable scattered power are simultanesouly excited, mixing with the anopole
and leading to a non-negligible total scattering cross section. Here we show
that for homogenous dielectric nanospheres, radial anisotropy can be employed
to significantly suppress the other multipole excitation, which at the same
time does not compromise the property of complete scattering cancallation
between Cartesian electric and toroidal dipoles. This enables an elusive pure
anopole excitation within radially anisotropic dielectric nanospheres, which
may shed new light to many scattering related fundamental researches and
applications.Comment: Invited submission with four figures and ten pages. Comments welcome
Structure-Induced Reversible Anionic Redox Activity in Na Layered Oxide Cathode
Anionic redox reaction (ARR) in lithium- and sodium-ion batteries is under hot discussion, mainly regarding how oxygen anion participates and to what extent oxygen can be reversibly oxidized and reduced. Here, a P3-type Na0.6[Li0.2Mn0.8]O2 with reversible capacity from pure ARR was studied. The interlayer O-O distance (peroxo-like O-O dimer, 2.506(3) Ă…), associated with oxidization of oxygen anions, was directly detected by using a neutron total scattering technique. Different from Li2RuO3 or Li2IrO3 with strong metal-oxygen (M-O) bonding, for P3-type Na0.6[Li0.2Mn0.8]O2 with relatively weak Mn-O covalent bonding, crystal structure factors might play an even more important role in stabilizing the oxidized species, as both Li and Mn ions are immobile in the structure and thus may inhibit the irreversible transformation of the oxidized species to O2 gas. Utilization of anionic redox reaction (ARR) on oxygen has been considered as an effective way to promote the charge-discharge capacity of the layered oxide cathodes for lithium- or sodium-ion batteries. The detailed mechanism of ARR, in particular how crystal structure affects and coordinates with the ARR, is not yet well understood. In the present work, a combination of X-ray and neutron total scattering measurements has been performed to study the structure of the prototype P3-type layered Na0.6[Li0.2Mn0.8]O2 with pure ARR. Unique structural characteristics, rather than prevailing knowledge of covalency of metal-oxygen, enable the stabilization of the crystal structure of Na0.6[Li0.2Mn0.8]O2 along with the ARR. This work suggests that reversible ARR can be manipulated by proper structure designs, thus to achieve high lithium or sodium storage in layered oxide cathodes. For P3-type Na0.6[Li0.2Mn0.8]O2 with relatively weak Mn-O covalent bonding, crystal structure factors play an important role in stabilizing the oxidized species, inhibiting the irreversible transformation of the oxidized species to O2 gas. The finding is important for better design of layered oxide positive materials with higher reversible capacity via the introduction of a reversible anionic redox reaction
The Contribution of Population Health and Demographic Change to Economic Growth in China and India
We find that a cross-country model of economic growth successfully tracks the growth takeoffs in China and India. The major drivers of the predicted takeoffs are improved health, increased openness to trade, and a rising labor force-to-population ratio due to fertility decline. We also explore the effect of the reallocation of labor from low-productivity agriculture to the higher productivity industry and service sectors. Including the money value of longevity improvements in a measure of full income reduces the gap between the magnitude of China's takeoff relative to India's due to the relative stagnation in life expectancy in China since 1980.aging, health, retirement
Determination of the superconducting gap in near optimally doped Bi_2Sr_{2-x}La_xCuO_{6+\delta} (x ~ 0.4) from low-temperature specific heat
Low-temperature specific heat of the monolayer high-Tc superconductor
Bi_2Sr_{2-x}La_xCuO_{6+\delta} has been measured close to the optimal doping
point (x ~ 0.4) in different magnetic fields. The identification of both a T^2
term in zero field and a \sqrt{H} dependence of the specific heat in fields is
shown to follow the theoretical prediction for d-wave pairing, which enables us
to extract the slope of the superconducting gap in the vicinity of the nodes
(v_{\Delta}, which is proportional to the superconducting gap \Delta_0 at the
antinodes according to the standard d_{x^2-y^2} gap function). The v_{\Delta}
or \Delta_0 (~ 12 meV) determined from this bulk measurement shows close
agreement with that obtained from spectroscopy or tunneling measurements, which
confirms the simple d-wave form of the superconducting gap.Comment: 5 pages, 4 figures, 1 tabl
Bicritical and tetracritical phenomena and scaling properties of the SO(5) theory
By large scale Monte Carlo simulations it is shown that the stable fixed
point of the SO(5) theory is either bicritical or tetracritical depending on
the effective interaction between the antiferromagnetism and superconductivity
orders. There are no fluctuation-induced first-order transitions suggested by
epsilon expansions. Bicritical and tetracritical scaling functions are derived
for the first time and critical exponents are evaluated with high accuracy.
Suggestions on experiments are given.Comment: 11 pages, 8 postscript figures, Revtex, revised versio
Density fingerprint of giant vortices in Fermi gases near a Feshbach resonance
The structure of multiply quantized or giant vortex states in atomic Fermi
gases across a Feshbach resonance is studied within the context of
self-consistent Bogoliubov-de Gennes theory. The particle density profile of
vortices with flux quanta is calculated. Owing to discrete
branches of vortex core bound states, inside the core the density oscillates as
a function of the distance from the vortex line and displays a non-monotoic
dependence on the interaction strengths, in marked contrast to the singly
quantized case, in which the density depletes monotonically. This feature,
never reported so far, can make a direct visualization of the giant vortices in
atomic Fermi gases.Comment: 4 pages and 5 figures; Published version in PR
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