25,500 research outputs found
Strong photo-absorption by a single quantum wire in waveguide-transmission spectroscopy
We measured the absorption spectrum of a single T-shaped, 14x6 nm
lateral-sized quantum wire embedded in an optical waveguide using
waveguide-transmission spectroscopy at 5 K. In spite of its small volume, the
one-dimensional-exciton ground state shows a large absorption coefficient of 80
/cm, or a 98 % absorption probability for a single pass of the 500-um-long
waveguide.Comment: 4 pages, 3 figure
Generarized Cubic Model for BaTiO-like Ferroelectric Substance
We propose an order-disorder type microscopic model for BaTiO-like
Ferroelectric Substance. Our model has three phase transitions and four phases.
The symmetry and directions of the polarizations of the ordered phases agree
with the experimental results of BaTiO. The intermediate phases in our
model are known as an incompletely ordered phase, which appears in a
generalized clock model.Comment: 6 pages, 4figure
Exact results for the 1D interacting mixed Bose-Fermi gas
The exact solution of the 1D interacting mixed Bose-Fermi gas is used to
calculate ground-state properties both for finite systems and in the
thermodynamic limit. The quasimomentum distribution, ground-state energy and
generalized velocities are obtained as functions of the interaction strength
both for polarized and non-polarized fermions. We do not observe any demixing
instability of the system for repulsive interactions.Comment: 12 pages, 4 figures, better comparison with hydrodynamic approach,
typos corrected, references added, improved figure
Room-temperature excitonic absorption in quantum wires
We measured absorption spectra of T-shaped quantum wires at room temperature
using waveguide-transmission spectroscopy. Strong and narrow room-temperature
one-dimensional-exciton absorption peak was observed, which shows peak modal
absorption coefficient of 160 cm per 20 wires with -factor of
, width of 7.2 meV, and strong polarization anisotropy.Comment: 3pages, 3figure, 1tabl
Imaging of emission patterns in a T-shaped quantum wire laser
Spatially and spectrally resolved microscopic images of spontaneous and
stimulated emissions are imaged at the mirror facets of a GaAs T-shaped quantum
wire laser with high uniformity. Laser emission from the one-dimensional ground
state reveals a circular image located at the core of a T-shaped optical
waveguide but significantly smaller in area than the low power spontaneous
emission from the same waveguide. These images unambiguously allow assignment
of all spontaneous and laser emissions to the wire ground state and respective
intersecting wells in the structure.Comment: 4 pages, 3 figure
Dynamic Emotional Faces Generalise Better to a New Expression but not to a New View
Prior research based on static images has found limited improvement for recognising previously learnt faces in a new expression after several different facial expressions of these faces had been shown during the learning session. We investigated whether non-rigid motion of facial expression facilitates the learning process. In Experiment 1, participants remembered faces that were either presented in short video clips or still images. To assess the effect of exposure to expression variation, each face was either learnt through a single expression or three different expressions. Experiment 2 examined whether learning faces in video clips could generalise more effectively to a new view. The results show that faces learnt from video clips generalised effectively to a new expression with exposure to a single expression, whereas faces learnt from stills showed poorer generalisation with exposure to either single or three expressions. However, although superior recognition performance was demonstrated for faces learnt through video clips, dynamic facial expression did not create better transfer of learning to faces tested in a new view. The data thus fail to support the hypothesis that non-rigid motion enhances viewpoint invariance. These findings reveal both benefits and limitations of exposures to moving expressions for expression-invariant face recognition
Spin-Wave Theory of the Spiral Phase of the t-J Model
A graded H.P,realization of the SU(2|1) algebra is proposed.A spin-wave
theory with a condition that the sublattice magnetization is zero is
discussed.The long-range spiral phase is investigated.The spin-spin correlator
is calculated.Comment: 17 page
Embedding the Texture of the Neutrino Mass Matrix into the MaVaNs Scenario
We have embedded the texture of the neutrino mass matrix with three families
into the MaVaNs scenario. We take the power-law potential of the acceleron
field and a typical texture of active neutrinos, which is derived by the D_4
symmetry and predicts the maximal mixing of the atmospheric neutrino and the
vanishing U_{e3}. The effect of couplings among the dark fermion and active
neutrinos are studied by putting the current cosmological data and the
terrestrial neutrino experimental data. It is found that the neutrino flavor
mixings evolve as well as the neutrino masses. Especially, U_{e3} develops into
the non-vanishing one and \theta_{atm} deviates from the maximal mixing due to
couplings among the dark fermion and active neutrinos.Comment: Sections 3 and 4 are changed and one table is added. 16pages and 2
figure
Bosonic Helium droplets with cationic impurities: onset of electrostriction and snowball effects from quantum calculations
Variational MonteCarlo and Diffusion MonteCarlo calculations have been
carried out for cations like Li, Na and K as dopants of small
helium clusters over a range of cluster sizes up to about 12 solvent atoms. The
interaction has been modelled through a sum-of-potential picture that
disregards higher order effects beyond atom-atom and atom-ion contributions.
The latter were obtained from highly correlated ab-initio calculations over a
broad range of interatomic distances.
This study focuses on two of the most striking features of the microsolvation
in a quantum solvent of a cationic dopant: electrostriction and snowball
effects. They are here discussed in detail and in relation with the nanoscopic
properties of the interaction forces at play within a fully quantum picture of
the clusters features
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