206 research outputs found
Structural determination and electronic properties of 4d perovskite SrPdO3
The structure and ground state electronic structure of the recently
synthesized SrPdO perovskite [A. Galal {\em et al.}, J. Power Sources, {\bf
195}, 3806 (2010)] have been studied by means of screened hybrid functional and
the GW approximation with the inclusion of electron-hole interaction within the
test-charge/test-charge scheme. By conducting a structural search based on
lattice dynamics and group theoretical method we identify the orthorhombic
phase with space group as the most stable crystal structure. The
phase transition from the ideal cubic perovskite structure to the one
is explained in terms of the simultaneous stabilization of the
antiferrodistortive phonon modes and . Our results indicate that
SrPdO exhibits an insulating ground state, substantiated by a GW gap of
about 1.1 eV. Spin polarized calculations suggests that SrPdO adopts a low
spin state
(), and
is expected to exhibit spin excitations and spin state crossovers at finite
temperature, analogous to the case of 3 isoelectronic LaCoO. This would
provide a new playground for the study of spin state transitions in 4 oxides
and new opportunity to design multifunctional materials based on 4
building block
Time changes of symmetric diffusions and Feller measures
We extend the classical Douglas integral, which expresses the Dirichlet
integral of a harmonic function on the unit disk in terms of its value on
boundary, to the case of conservative symmetric diffusion in terms of Feller
measure, by using the approach of time change of Markov processes.Comment: Published at http://dx.doi.org/10.1214/009117904000000649 in the
Annals of Probability (http://www.imstat.org/aop/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Scatterer induced mode splitting in poly(dimethylsiloxane) coated microresonators
We investigate scatterer induced mode splitting in a composite microtoroidal
resonator (Q ~ 10^6) fabricated by coating a silica microtoroid (Q ~ 10^7) with
a thin poly(dimethylsiloxane) layer. We show that the two split modes in both
coated and uncoated silica microtoroids respond in the same way to the changes
in the environmental temperature. This provides a self-referencing scheme which
is robust to temperature perturbations. Together with the versatile
functionalities of polymer materials, mode splitting in polymer and polymer
coated microresonators offers an attractive sensing platform that is robust to
thermal noise.Comment: 9 pages, 3 figures, 15 reference
Estimation of Purcell factor from mode-splitting spectra in an optical microcavity
We investigate scattering process in an ultra-high-Q optical microcavity
coupled to subwavelength scatterers by introducing "splitting quality" Qsp, a
dimensionless parameter defined as the ratio of the scatterer-induced mode
splitting to the total loss of the coupled system. A simple relation is
introduced to directly estimate the Purcell factor from single-shot measurement
of transmission spectrum of scatterer-coupled cavity. Experiments with
polystyrene (PS) and gold (Au) nanoparticles, Erbium ions and Influenza A
virions show that Purcell-factor-enhanced preferential funneling of scattering
into the cavity mode takes place regardless of the scatterer type.
Experimentally determined highest Qsp for single PS and Au nanoparticles are
9.4 and 16.19 corresponding to Purcell factors with lower bounds of 353 and
1049, respectively. The highest observed Qsp was 31.2 for an ensemble of Au
particles. These values are the highest Qsp and Purcell factors reported up to
date.Comment: 5 Pages, 4 Figures, 12 Reference
Regional Finance and Regional Disparities in China
China’s growth has been spectacularly high and persistent over the last few decades. However, there have been regular expressions of concern about the uneven distribution of the benefits across regions and, at times, it has been asserted that the regional distribution of available investment funds has played an important role – national financial institutions (mainly state-owned banks) have redirected deposits from the inland to loans to large institutions in the more prosperous coastal regions. At the same time, smaller regionally-focussed institutions are likely to improve the distribution of funds. We use a panel data set disaggregated by province for the years 1986 to 2004 to test these propositions. We employ recent panel unit roots and cointegration tests using data for state-owned bank loans as well as loans by rural credit cooperatives. We find that financial disparities are related to output disparities, that this relationship is positive, that it is stronger for rural credit cooperatives than for state-owned banks and that this relationship is causal in both the long and short runs. A reduction in financial disparities can be expected to lead a narrowing of output disparities in the short run and in the long run with the effect being larger for rural credit cooperatives than for state-owned commercial banks.regional disparities, panel econometrics, regional finance, China
Exceptionally strong magnetism in 4d perovskites RTcO3 (R=Ca,Sr,Ba)
The evolution of the magnetic ordering temperature of the 4d3 perovskites
RTcO3 (R=Ca,Sr,Ba) and its relation with its electronic and structural
properties has been studied by means of hybrid density functional theory and
Monte Carlo simulations. When compared to the most widely studied 3d
perovskites the large spatial extent of the 4d shells and their relatively
strong hybridization with oxygen weaken the tendency to form Jahn-Teller like
orbital ordering. This strengthens the superexchange interaction. The resulting
insulating G-type antiferromagnetic ground state is characterized by large
superexchange coupling constants (26-35 meV) and Neel temperatures (750-1200
K). These monotonically increase as a function of the R ionic radius due to the
progressive enhancement of the volume and the associated decrease of the
cooperative rotation of the TcO6 octahedra.Comment: 4 pages, 3 figure
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